I routinely use similar product here in oz to paint my boats, when dealing with old fibreglass boats that are no longer show ponys I don't see the need for expensive resprays that don't last anyway, here they generally use a 2 pak urethane paint on fibreglass, but factory made boats aren't painted like this they use polyester gelcoat to colour the fibre glass and this is a very hard wearing finish, I am a painter by trade though retired so I have the know how to do it but I just use an epoxy based enamel metal paint, as said there glossy as anything and given time in the sun like we have they bake real nice and hard and will last for years and there easy to repaint / touch up / I use a fine wet and dry sand paper and rub the surface back until the finish is dull, I use polyester based auto filler to repair and if primer is needed I use the epoxy enamel primer in the spray pak, a final rub down and then I use penetrol to key the surface, then Im ready to paint, I use a good quality paint brush and a narrow fine mo hair roller, u can use products to retard the drying process, I always work to a three coat system this is just the finish coats, this finish is good above or under water and is easy to clean down again when the need to repaint.