Should I use proper masking tape of will sellotape do the job?
It sticks on well but allows repositioning without affecting adhesion. I left on on for several days after painting and it peeled off without any paint having crept under the edges so a good level line was achieved. It tears easily so a little care is needed when removing or the edge of the tape which has a coat of dry paint on it can be left behind and needs to be gently picked off.I'd certainly use this product again.
I tried using sellotape once - don't bother trying to save few pounds, this does the job much better.