Slightly tricky to work with, particularly if you’re wanting it to look neat - not a job you can rush. I was doing a small motorbike exhaust and wanted it to be tidy, took me about an hour including masking up the edges, removing loose rust etc. Apply to cold exhaust. I allowed a good 24hrs to dry including running the engine at tickover for 5mins.
It’s like stringy thick blu-tac. It dries a dull silver / light grey colour (lighter than it is when you take the lid off the pot).
Use PVC gloves. To tidy up the edges, lick your finger and manipulate in to place. Works really well, thoroughly recommended.