You're unlikely to gt much of anything to adhere to that paint, although I'm not really sure what you mean by "regular paint". Regular for houses, regular for automobiles, or regularly found in basements? (g) I think you need to get a fiberglas safe stripper to aid you in your sanding efforts. A pressure washer judiciously used may help. You will certainly have no luck with trying to spray gel coat over it. And I'd be skeptical of any primer claims to bond with it as a prep for a marine paint.
I think you'd find Don Casey's Complete Illustrated Guide to Sailboat Maintenance a very helpful and comprehensive book in helping you restore this boat.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.