Pics would be good for an idea of what you be doin...
The surface needs to be very rough if you want it to stick worth a damn, I use 40 grit sanding discs and MEK or acetone to clean up all the residue you can, oil and the wax from the origional fiberglass are the biggest hurdles (wax is used to make finishing resin) make sure and get it as wet as possible without making a big fricken mess...
Good Luck!
GT