Here are a couple more tips that have worked for me. Cut out a number of cross sections of your hull at regular intervals from thin plywood, stiff cardboard, or whatever your favorite material. Sandwich these between your layers of foam as a guide to your carving. You just sand down until you see the edge of the sections. You can use drywall compound to fill in any uneven areas to get a smooth finish. The idea is to get your foam plug as close as possible to your final shape, minus of course the anticipated thickness of your glass laminate. Then you do not want to apply your resin to thickly. This will avoid a lot of final sanding. Also, it helps to mount your foam sandwich on a central rigid rod to keep everything in alignment.
If you plan to use polyester resin rather than epoxy, you can coat the foam plug with several coats of clear polyurethane. This keeps the resin from melting the foam, which it would otherwise do. You can follow the polyurethane with several alternate coats of Poly Vinyl Alcohol (PVA) and liquid wax to form a mold release. Then you can just pop the plug away from your finished piece rather than melting it with acetone. This is handy for items like conning towers, etc. where the finished piece can be lifted off the plug. You can then reuse the plug. Experiment.
George "Crazy Ivan" Protchenko
“There are the assassins, the dealers in death; I am the Avenger!”-Nemo
"I'm disinclined to acquiesce to your request; means No!"-Capt.Barbossa