Rustoleum Enamels are pretty good. They are fuel tolerant without a topcoat, but require a 2 week cure time before use.
I have used "stop rust," "painters touch," and "professional" in gloss with good results.
Grey Rustoleum "Professional" primer seems the best. It cures very quickly to a state that sands easily, a couple hours.
The "Painter's Touch X2" primer I found annoying as it would ball up and clog the sandpaper if not cured enough. After about 2 days of cure it sanded pretty well. Since it comes in white, grey, black, and red I will likely end up using it again.
Both primers can be used to fill the grain, however using lightweight spackle fills the grain much much MUCH faster prior to priming.
My fuel proof test is to use 1/2a fuel, 25% nitro, and apply it with a paper towel to the cured paint. Cover the paper towel with plastic and let sit an hour. Paint should not come off with light rubbing. Paint is allowed to discolor when wet like this, it will return to normal color overnight.
Cured off enamel can be sealed with polyurethane varnish. This is also available in a rattle can. Make sure it is the STINKY type as the water born types are removed by alcohol. Some have an amber color to them, others are clear. Polyurethane seems to be suitably cured after a couple days. Polyurethane can also be used on bare wood with excellent results. (use colored markers and then poly for quick simple kid-friendly decorating)
Be very careful if you are using dope with enamels. Enamels can go over aged dope. As long as only enamels will be used afterwards it will be fine. I have not tested polyurethane over enamel over dope. I know that Balsarite over enamel over dope creates an unbelievable mess since the dope softens and sloughs the enamel.
Using Minwax polycryllic underneath the enamel seems fine. I have only done this on two models, built together. One is destroyed and the other is overweight.
Speaking of overweight, enamels, polyurethane, and polycryllic are heavier coatings than dope. This means that care must be taken in application so not too many layers are used. On 1/2a limit to 1 coat only of enamel color.
Phil