I am the owner of a painted hull. I did not paint it and do not know what was used but I hate it. To get rid of the dull look that your hulls have wet sand them with 600 grit then polish them with polishing compound. patch your holes and then carefully apply gelcoat as it dries hard and a good belt sander is needed for the first sanding. Fiberglass is pourus and will absorb water, gelcoat does not (as much) but is a pain to sand. I have never tried urathane on a boat but after working on an oak platform bed for the kids urathane is also not my favorite. it is sticky, dries slow and can be soft days later.(fingerprints) If I was going to paint a boat I think epoxy paint would work. they use it in chemical plants on metal to protect it from the toxic air and on deep sea oil rigs.