GREETINGS EARTHLINGS I have painted afloat but It is not enjoyable when on small-boat and lean in to get a bit of pressure the boats wants to go the other way so to componsate this you make the roping tighter wich then marks the newly appied paint.
Regarding the boot top DO NOT SCORE THE LINE! Just make sure that you have a watertight edge on this by pressing home with a plastic of rubber hard roller this stops the paint infulltrating the masking tape. (DO NOT MIX ALL THE PAINT IN ONE GO.) THIS WILL EXTEND YOUR WORKING TIME GO SAFE