Rustoleum is a good finish for diesels too. I had a real disaster with Rustoleum and glow fuel but with diesel there is absolutely no deterioration and it cleans up to like new condition. I use clear nitrate to prime and seal.

I've used Polyspan, Airspan, and Koverall. The first two are very light and the first is also very strong. Airspan is OK but it will tear. Koverall finishes are not as heavy as you might think. I'm about to try Thai Silks which should be fine for small models.

Now here's an ugly truth--every film covered plane I've seen at our club field, no matter how great it looked at it's debut, looks lousy a few years later due to wrinkles that finally won't shrink out any more, lifting edges and scratches. Paint is worth it to me no matter what the fuel. And the nice thing about small planes is that it is really no big deal to paint them.

Jim