I am just now researching the products and methods for the same project on my boat. It seems that each finish product will have its own recommended steps, products, and procedures to ensure proper adhesion and longevity. I am considering
Awlgrip for the topsides and they have a whole set of "directions" available. Haven't researched bottom
paints but don't skimp as the labor is the big expense! Bondo absorbs water as does raw fiberglass resin. Find something else! Check online at Anzam Yacht Refurbishing for a great article on how-to Painting Topsides. It has some wisdom that will apply tothe bottm as well. Good luck....