Airbrush rookie

Biggest thing is practice.  Do not go after a good model without practicing some airbrushing of scrap plastic.  Planes are often flat finish, cars and trucks gloss.  The latter is harder to paint than the flat stuff, so after some practice with some flat paint, try it on some military plane kit.  Experiment with thinning ratios and pressures. I use Testors enamel and start with a 1:1 thinning ratio and about 20 psi for flats, 15 for gloss.

For someone who's using an airbrush for the first time, use the brand thinner to use with the brand of paint you're using for now. - ie: Tamiya acrylics, use Tamiya brand thinner, Model Master Acrylics use Testors Universal Acrylic thinner, etc... Once you get the basics down to pat, try experimenting with cheaper methods of thinning paint and cleaning your airbrush.

The two posts above pretty much says it all.