Lowes Brush Cleaner
You might try the following to remove paint from gel coat. First try the weakest, Lowes "Klean Strip" brand Brush Cleaner. I use this to clean topsides and cockpit gel coat each season, comes out like new. Also try Lacquer Thinner, Acetone or M.E.K. , each being a little stronger than the next. If the Brush Cleaner doesn't do the job, try Acetone. I use it all the time on Gel Coat.
Jack F Stewart
1993 C36 #1233 "Windancer"
Port Clinton, OH