In my time, I have in South London and Bournemouth sold many many cars and have taken tips from the professionals themselves as well as developing my own way of making virtually any car gleam.
Now, many cars out there are past their prime, why bother, its an old scrapper, people will say but I have always taken these old scrappers and as long as the top paint is pretty much undamaged, can breathe new life into the saddest of vehicles and it does reflect in the price of your sales, if it looks better than before, if it looks halfway decent, then the price is always higher as a result when you sell.
There are two ways at looking at this, when you have a newish car, people expect it to be newish inside and out and you move accordingly to that, however....
If you have an older car, then expectations change because a gleaming engine and gearbox on a 150,000 mile Sierra, many will be suspicious and expect the engine to leak like a sieve so it is best to act accordingly to that as well.
All my vehicles, bought and sold end up leaving my ownership if I am lucky with paintwork looking like wet glass and boy does that make a difference when people buy.
Lets wash the car then...
Now this may sound crazy but the first thing you can do, to help you is to take your car down the jet wash and give the wheel arches, the lower portion of the car a damned good blasting with the lance or if you have a lance attachment for your hose, get rid of the built up mud and grime in the arches, grilles, under the sills and rear underhang.
Many people will want to see under there and get turned off by probing and getting a face full of dried mud or if you live in the country dried horse and cow manure, you can also give these areas a visual inspection for rust and such and be ready for this if it comes up in the conversation (nothing is more disastrous than your potential buyer discovering something bad and don't believe that you didn't know and think you are trying to palm off a wreck)
Now we have cleaned the car with the lance or hosepipe and we begin by having a medium-hot bucket of car shampoo. (avoid one with car wax added, just a simple car shampoo will suffice)
Take your large sponge and working from the roof down to one side, do each section, piece by piece but in such a way that you work downwards otherwise if you start from the sill upwards, any mud and dirt is just literally respread over clean paintwork making it look bad from the beginning.
Do the areas under the bumper line and wheels last as wheels invariably have grimed in brake dust and I use a dustpan brush dipped in the bucket to really get into those creases and rinse off with the sponge.
Rinse your sponge out once you are happy the car has been scrubbed to your satisfaction, bear in mind also to not be too harsh on rusty areas or paint scabs on older cars, be gentle with these areas and don't allow flakes of rust to embed in your sponge as they will scratch your paintwork quite badly.
Rinse your sponge and bucket right out until they are free from shampoo residue and fill your bucket up with nice clean cold water, most people chuck water over their cars but not only is this wasteful it can end up with dirt being respread around the car from the gutter areas for instance, by lathing the car with your sponge and cold water, maybe even two buckets of cold water for a larger car, this allows your to really spot the grimed in dirt but also allows for a better finish overall with less smears.
You are basically washing your car again but with clean, copious amounts of cold water, I have found that this really helps in the later stages of cutting and polishing as the T cut seems easier to take off because the dirt is throughly sluiced off and clean paint left behind.
Again work from the roof, down to a side of the car, round to the back, along the other side and finish on the front, then do the underbumper areas and finish off rinsing the wheels and tyres and that should be your car washed.
Now for this area, you will need a few NEW yellow dusters which are quite easily available from most supermarkets, some cutting agent like T-Cut (if your car is less than two years old, I would not recommend using normal T-Cut but a gentler new car compound as many cars paint is still not cured at 2 years of age), if your car is metallic in paint then a metallic cutting compound is more desireable as it is finer, and of course your wax polish.
I use Turtle Wax hard shell wax polish as a favourite for me because it delivers a very good, long lasting, hard and hard to scratch surface which also can be livened up by simply washing the car making it shine once again, it is also layerable and currently the Fiesta has something like 25 layers of wax which makes the 1989 car look like new.
T-Cut CAN damage your paintwork and should be applied sparingly with a yellow duster in small patches at a time, avoid using circular motions and try and follow the cars contours and lines as much as possible, if you start to see spotting, then turn the cloth over that you are using to apply the cutting agent with and sometimes the most stubborn of dullness may need a bit of pressure when rubbing the agent off.
Avoid getting the T-Cut and polish on plastics as it stains the plastics making it look unsightly, practice with the agent until you get a clear shiny fiinish on the paint itself and by visually looking along the panel you can see that no film, oxidisation is left and you have a clear shine across the panel itself.
When removing the cutting agent from your paintwork, it is worth remembering that if the cloth starts to drag (your taking off cloth) just stand away from the car, give it a good shake and flip the cloth over so a fresh side is taking the cutting agent off, by doing this frequently, you stop the cloth clogging with dried agent which can inflict scores and scratches to your paintwork.
When your car is done all over and is to your satisfaction (you may on heavily dulled cars have to do 2 cuts BUT metallic painted cars should be avoided in multiple cuttings as the lacquer is a very thin coat and you can literally take the shine off a metallic car by too many cuttings) you can move onto your polish, which should be in a tin or squeezy bottle.
The trick to a good polish is to get a consistent and thorough filmy haze 100% across the panel, the haze indicates that the wax polymer is covering that paint, car wax is very easy to apply but the devil to get off black bumpers and trims so apply carefully, unlike cutting agent, car wax can be applied in one go but avoid direct sunlight as it causes the wax to dry before attaching itself to the paint thus dulling the potential shine.
Apply an even and sparing coat across the vehicle avoiding window rubbers and black/plastic trims and wait for the wax to haze up (whitish powdery look) once it has done this, take a fresh yellow duster, fold it into a pad and rub the haze from the car, turn this pad over frequently and shake it out when the rubbing seems to catch, blow flakes of polish and dust from the car and when the car is done, take another duster and gently flow the car panel with it to remove any smaller pieces of dust and your car should be polished.
If the polish isn't as shiny as you expected, apply another coat, which will deepen the shine considerably as well as add more protection to the paint from stonechips, cats claws and bird doings.
When you have a car that has large surface rust areas or scabs of paint, it is best to carefully cut and polish as close to them with out getting the cloth onto them as polish especially makes the rust turn white and looks worse than if left alone.
You can also polish your wheels if clean enough and maybe alloys, use a bit of metal polish on the chrome nuts and normal wax on the wheel face itself and will add a nice lustre to that alloy or wheel trim.
Don't go and spend a fortune on glass cleaners when a bottle of malt vinegar costs about 27p from the supermarket and old newspapers are easy to find, vinegar and newspaper is in my mind far, far superior than any branded cleaner as it is cheap and it is EFFECTIVE!.
Basically with your vinegar and newspaper, scrunch up a newspaper page, pour a dab of vinegar on it and scrub the window until the smears have gone, leaving spotless glass, discard the used paper and with a fresh page do another pane and so forth and you will have a very clean glass indeed.
It can be used interior or exterior and does not smear when wet unlike some branded products and apart from a slight vinegary smell inside the car which doesn't last long, it does do the job.
Ashtrays can let a car down, even if its emptied, an ashtray that is grey with ash may make a non smoking buyer walk away, so take it out with any other ashtrays and wash them up in the sink with a bit of fairy liquid and hot water, use an old toothbrush for heavily crusted examples, dry with rags or newspapers so that the black interior of the ashtray is clean and ash free.
Dashboards can also let a car down and a good wipe down with some specially bought wipes or cockpit spray can work wonders, get into the vents, louvres, door pockets, fittings etc and the centre console, also using a cloth, clean the glass on the instruments and other displays, get right into the corners and edges so that its 100% clear and looks clean and fresh.
Carpets hoovered thoroughly will always look better than when the buyer is looking down the crevices of the seats and spotting loads of old sweet wrappers, dirt and dust etc, so using the thin wand tool of your vacuum, get into those nooks and crannies.
Floor mats are cheap today and a set of worn out floor mats will look awful in a otherwise nice car, rubber ones can be bought very cheaply, sportier ones are more expensive but only really look the business in a sporty car, if they aren't worn, then take them out and beat them against a wall to remove caked in dirt and grime and finish off by vacuuming thoroughly especially as not many people know that fleas can be picked up on our shoes and deposited in the mats if you walk across a grassed area where cats, dogs and foxes may frequents, imagine the disaster that your buyer may have when getting bitten by fleas you did not know were in your car.
Interior plastics such as sill protectors can also be cleaned and look better cleaned than dirty or grimy, a bit of soapy water and a sponge squeezed out will work wonders here too.
Seat belts can get "hairy" where multiple small nicks and frays make it look a bit hairy, this is a trick I picked up from a scrapyard I worked at BUT it must be done carefully for your own safety as the seatbelt is a very good safety device and will stop you dying. Taking a small gas lighter and lighting it, by introducing the flame NEAR the fray will cause it to shrivel without impeding the security of the webbing itself, this is not something I would recommend and as seatbelts aren't that dear, if its THAT bad then maybe a new set is the answer. (this is at your own risk and no responsibility assumed this end)
Twisted seatbelts are not only dangerous but look awful so carefully pull out the whole belt and by folding the belt webbing in the right way, you can pull it through the buckle and thus untwist it. Badly twisted belts may need more than one of this.
So now, your car looks good on the outside and the inside as well, tears and holes in seats by the way can with a curved needle and closely matching thread or wool be darned to repair holes and splits, spray applications are also very good at cleaning stains but not as good as a carpet shampooing type machine such as a Vax but the seat will be damp for quite a while and cannot be used on cars with heat pads or air bags.
Engine Bay and Boot.
The boot area can let a car down, for the want of a wipe with a soapy sponge, the plastic areas inside the boot, a damned good vacuum and making sure the spare wheel well is clean and dry as opposed to a boot full of leaves, junk and mud, it sure makes a difference to clean it out.
At this point it might also be useful to WD40 your boots hinges and locks and why not spray a bit of WD40 on the rest of the cars hinges and locks for the doors and even the bonnet hinges, it stops squeaks, reduces wear and can even clean a dirty area.
The engine bay as I explained further back can make or break a car, if you have a newish car that is filty inside, loads of oil stains and dirty marks all over, then that deducts selling points for your vehicle, unless you are going to factor in a reduction for example for a slightly leaking rocker cover, then it is more better in the long run to just change the gasket or in some cases, use silicon rubber to seal certain covers instead. You can if careful jetwash your engine bay but to do this you MUST protect ALL electrical connections which on a modern engine is no mean feat and as some ECU's have atmospheric sensors, it would not be good for them to force at 80PSI a stream of cold water through the sensors orifice and the mutliplugs also cannot get wet either.
Steam is also a good medium for cleaning and I have used to great effect the JML steam wand thingy as it cuts through grime and dirt whilst not soaking electrics BUT again you have to beware heat damaging components and such.
The inner wings are on older cars usually dirty and not many people realise that these areas can be cut with an agent and polished, this makes the bay look nicer than grimed in road dust and a dull finish, I did this on a Triumph Dolomite I had restored fully and waxed it and as the engine and everything else was as factory fresh I used something that Holt's made at that time called Motorcycle Engine Lacquer and coated the whole area which made the engine area look as good as the outside of the car which was immaculate.
Battery tops, air cleaners and plastic tubing and trunking always benefit from a wipe down with a damp cloth to remove dirt and dust, also take a look at the underside of the bonnet and see if there is a buildup of oily grime there as removing that freshens the area no end.
It pays also to clean the rocker cover, if for instance it is a painted Ford CVH cover, then some WD40 and a cloth will do the trick admirably, alloy covers can be polished with metal polishes and plastic can always be wiped with a cloth.
Engine and VIN plate numbers should always be clean and easy to read so bear that in mind, basically in the bay, if something looks unsightly to you, then it will to a buyer and act accordingly.
Lastly as a tip for the wise, when selling a car, honesty will always triumph over hiding something, by researching how much something will cost to repair will also pay as people will walk away if they spot the head gasket is going and you didn't say anything but a head gasket is not always a fortune on all cars (about a fiver for a Metro A+ and an hours easy work)
I am of the persuasion to say that a fault can be portrayed as the doom of the car or something easily fixed and that is where your usual bargain hunter comes in because he is not afraid of putting new pads on or even something a bit more involved if the cost of the vehicle plus the repairs is still a bargain than buying something without that fault.
And when selling that car, list the bad points but also list any positive points, the fact that it starts on the nose every morning, hot or cold is a positive, any new or recent parts fitted is a positive, any service history is a positive, work out the mileage for the car and as long as it has done less than 10,000 miles average a year then that too is a positive, mileage is not a factor for many cars as BMW's consider themselves "run in" at 150,000 miles, Mercedes are also cars with the potential for high mileage, VW's, even the old Fiesta Crossflow/Kent engine is capable of doing many hundreds of thousands of miles in its lifetime, what is the important factor is: are those miles done with regular oil changes and maintainance.
The problem is that when you list a car and fail to tell someone about something that could be interpreted as major or safety related, they really look askance at you and the question of are you a cowboy operator comes to mind, never take a chance on safety aspects, in all my time I have never sold a car with dodgy brakes or steering and the law now states that if you sell a car knowingly with a safety defect and the new owner kills someone you may be in the frame for manslaughter if that component fails.
Also avoid selling or buying in the rain, dusk or the dark, try if you are buying to see the car in normal daylight as fluroescent lights can hide a lot of problems with a cars exterior, if someone wants a test drive, ensure they are insured as again the law will hold you responsible for allowing the car to be driven by someone uninsured.
Payment by cash, cheque if they will wait for it to clear, Paypal if you don't mind the risk of a clawback at some stage and heinous fees the choice is yours, I mention the clawback thing, as people do this quite often, pay for something using the credit card, tell the credit card to claw back the money, Paypal refund and you have lost your money, Paypal will ALWAYS honour a refund even if you can prove that the person is telling a stack of porkies and Paypal will ALWAYS take the money regardless of your thoughts, wishes or even legal rights, so Paypal is good for buying BUT not always good for receiving large sums of cash which you can lose quite easily without retribution to the other party.
One last tip, when you sell a car, that big hole where the stereo used to be really is a turn off, nipping down the local scrappy and picking up a cheap cassette player even would bring up the selling points considerably, stereos aren't hard to wire in and there are plenty of sites out there with comprehensive information for the beginner audio fitter, even if you only wire the front speakers in, as long as its a tolerable sound, it sits better with the buyer who may want to fit their super duper stereo at some point but for the sake of a few pounds and ten minutes at the scrap yard, you could reward yourself with a better selling price.
I hope that this is of some use, I was inspired somewhat when a neighbours kid offered to hand wash my car and I was intrigued to see how he done it and after paying him, I washed the car, showing him how it was done and he was impressed and now has regular stints with people because unlike before they are quite pleased with their gleaming cars as opposed to the cars with dirty streaks running down 'em.
This isn't the end all of guides as no doubt others out there have their way of doing this equally as well and I have to admit that my way is good, efficient etc but there is always room for improvement.
You only get out what you put in, if you aren't bothered at getting an extra amount of money for your vehicle then this is not for you, but for those who are looking to sell their car for the first time will invariably pay someone £75 to get their car cleaned when in truth, they could do it themselves, have more fun, do a better job and save themselves the cost of a valet.