Honestly, I never picked up a book or even read/watched anything to teach me how to use an airbrush. I just grabed it outta the case, loaded some paint into it, and started messing around with it. Eventualy I figured it out, and now I can do all sorts of things with it, from painting model airplains to painting desinges on cars and trucks. All you have to do is "thin down" the paint to make it flow easly through the airbrush nozel. If your using a water based paint, use water to make the paint flow easer, and almost make it runny. If your using oils/enamels, you have to buy a certan thinner chemical to thin the paint.
There is no real differance between airbrush paint and car paint, other then the fact that car paint is more durrable and can take a far harder beeting. Other then that, its realy the same. It all depends on the type of paint. It could be soft/hard acrylic (soft for clothing, hard for models and whatnot), water based, oil, enamel or any other type you can think of. Normally for cars, its enamel based paints. There area also flat/matt, satin semi-gloss, and gloss paints. Flat/Matt being the lest shinny (no shine), and gloss being the shinniest. Cars are normaly painted gloss, but in the military, they are painted in flat, or "matt" colours.
There is also clear coat witch comes in Flat/matt, satin, semi-gloss and gloss aswell. Depending on what type of paint you use (Flat/matt, satin, semi-gloss, gloss), you use the same clear coat type as the paint.
Now, a word of the wise, NEVER put a coat of one typed base of paint, and put a differantly typed base of on top. For example, never put a oil based paint over a acrylic paint, or never put a gloss based paint over a flat based paint. The result will be the paint cracking and it leading to a horrable finish.
Its great what you can do with an airbrush. You can even do make-up! That could be a good skill for your sister(s)/friends, and trust me, they will love you for that (They can save hundreds of dollars, although you will all just spend the money you saved on a new pair of $2000.00 shoes LOL, just kidding!)
Also, you can clearly tell the guy uses multiply coats of clear coat.
Well, that prety much sums up everything. Any other help you need, just post and I will do my best to answer.