I can't for the life of me understand what the great mystery is about painting fiberglass. In houses we paint paper covered gypsum wallboard, concrete block basement walls, previously varnished hardwood kitchen cabinets, wooden exterior trim all of which are much poorer substrates than fiberglass. We paint wooden porch decks, railings and ceilings all with great success if we use good preparation methods. Why does painting a boat become such a mix of magic and alchemy?