I recently faced this problem when finishing my Nieuport 28. I used to love K&B Superpoxy, but that's gone, and their Ultrapoxy is lousy IMO. I ended up doing my seven color camo with Rustoleum, available at most hardware stores in a variety of colors that can be mixed to match just about anything. Very fuel proof, and non-catalyzed, so you can dump it back in the can when you're done. It's a little slow drying compared to the K&B, but not that bad. The finish, at least on my fabric, is more satin than gloss. I suppose you could spray flattner over it if too glossy.

Hag