If they've been waxed recently I would clean them first with FSR (Oxalic acid) or snobol( hydrochloric acid). Snobol cheaper. If it's been a year then I wouldn't worry about removing it other than washing the hulls with Dawn. I wouldn't use acetone. Old Gelcoat is pourus and the acetone will only wash the wax deeper into the surface.

I would sand with 80 grit. Sprayed gelcoat covers 80 grit sanding scratches so what's the point of using finer grits?? Why work harder than you have to.

Someone posted this a while back. Do some reading and pratice on something smaller before tackling the boat. gelcoating