Topside is just the name for marine-grade paint
designed to go on fiberglass--boats and our trailers flex a bit more than metal things like cars and aluminum trailers. So you want a paint
that will flex a bit as well. We would only us a marine enamel (primer and topside) paint on our fiberglass.
We used one coat of primer in most places...where Paul bonded or fiberglass filled we used two coats, sometimes, a small area painted right over the repair and then that was covered with an overall coat that went on everything.
then we used two coats of topside paint, both very thin and spread thoroughly with a small, "hot dog" foam roller (hot dog rollers have a covered end so you can get into small areas with the roller carrying paint).
Paul rolled it very carefully and diligently, to press out all the tiny paint bubbles. Some advocate a "roll and tip" method, which is where you roll first and then drag a "dry" brush over the surface to pop all the little bubbles. By the time Paul was done, there really were no bubbles, and the marine enamel "self-levelled" and whatever brush or roller strokes were apparent quickly smoothed out.
He sanded between every coat. The patch primer, the primer, the first and the 2nd coats of topside. So far he hasn't wet-sanded, and now that we have the decals on, I doubt he will.
The rub-on decals are "soft" and would be marred by sanding. But we may one day decide to try rolling some ZEP floor wax over it all--I hear six coats makes a lovely shine.
But we like the soft fiberglassy glow of the paint itself, and have had many compliments on it anyway.
The advantage of using Rustoleum is availability and cost and the relative softness of the paint (compared to "better quality marine enamels") is that when a rock chip or branch makes a mess, you can fairly easily put on some more paint and it will blend in easily. Paul has already filled some rock chips from our first six trips out.
Here's the real kicker--if you decided to use Durabak rubberized paint, those rocks would possibly bounce right off! We'd like one day to use some under the rig at least...but talk about pricey and hard to work with! And it has a shelf-life, once opened, of about a month., so their literature tells me. Maybe two--but certainly not a year. So our ability to use some leftovers for any mars would possibly mean buying more fresh rubber paint...though they do say you can put more on right over and it will blend in perfectly.
But so far it's sold
only by mail in our area (Seattle) and the shipping of a quart of touch-up paint is costlier than the paint itself.
Back to Rustoleum.
Love that red and white combo--sharp!
I'm sure you can thin the Topside marine enamel and spray it if you want to...and I agree, two coats make a better finish than one.
Being an obsessive sander helps, too!