We just started painting
our (yellow-orange!) interior fiberglass with regular Rustoleum (or Tremclad in Canada, I believe) yesterday. We...
1. sanded lightly with 120 grit
2. rolled on a coat of Kilz primer -- spray primer would have been smarter.
3. sanded again to get rid of the terrible roller texture
4. sprayed. Primer and paint are both white, so it only took two coats of spray to get full coverage -- we've used 2 cans of paint so far for two modules (the upper kitchen and one side of the dinette). Our hardware store had larger "33% more free!" cans for $4.99, so price is manageable so far.
Oh, and, we DO have the furniture all out of the trailer right now, so access is pretty easy. Having to work with everything IN the trailer would add a significant amount of prep/masking.
The finish is shockingly nice, especially for such minimal time and investment. Go for it!
I'll try to update with a picture or two later.