If you are covering open bay, rib framework and just looking for something fuel-proof to put on the bare wood, then Polyurethane varnish - such as Minwax, is fuel proof up to at least 40% nitro. Just brush it on or buy the spray cans and spray it - it comes in gloss and satin (semi-flat).

For a slab-wing, like a 1/2A Skyray, you can do the whole thing in varnish or spray with an enamel like Rustoleum, then use a coat of the varnish over the top. Rustoleum is 'kinda' fuel proof, but not 100%, and also it is heavy so go easy with it. Between the Rustoleum and the Lustrekote, they are pretty much the same as far as using the rattle-cans, though the Rustoleum will be a little cheaper and comes in more colors.

I have been tinting the varnish with artist's oil paint (comes in a tube, from art supply stores or craft stores). It gives a finish that is kind of 'candy apple' or transparent color. It goes well with a transparent film covering. You could even mix to get different shades. I have also used Rustoleum from the small cans meant for brushing to tint the varnish.

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Here is a picture of transparent blue monokote on the wings and a tinted Polyurethane varnish fuselage.