I have only worked with airbrushes themselves a few times but I have worked with full size sprayers used in car painting and 'airless' sprayers, and what I found mirrors what others have said. There are people on here who are likely experts, but here is my thoughts to get you started:
-Buy a good quality compressor, cheap compressors seem like a bargain but they aren't, my experience is that the cheap compressors end up causing more problems then they are worth (as always, others may have found cheaper ones that work great).
-Likewise with the airbrush. There are cheap knockoff airbrushes that look the same as Paasche and Badger but take it from me, they aren't worth it IMO, it is the internal components that make a difference and the cheap ones quite frankly are crap.
-Take the time to learn how to take the airbrush apart, do it dry when you get it, to where you can do it easily. Among other things you will see pretty easily where the problem areas are with them.
-One of the things I can't emphasize enough, and that is that you need to clean the unit thoroughly after ever use. Some might argue, but simply blowing water/soap (water based paint) or lacquer ,acetone, etc after use is not enough, found that out the hard way. It is why I recommend learning how to take it apart, there are parts inside that can accumulate paint and cause it to fail, the needle valve and even some of the components that help it maintain steady pressure. It actually isn't that hard. With full size spray guns every one in a while I would take them apart and soak the components in solvent, it saved me a lot of grief as well as routine cleaning
-The biggest key using sprayers is to learn the paint you are using and how much it needs to be thinned, and that varies with every paint. Paint manufacturers and the airbrush makers often have recommended ratios but those aren't always optimal.
Best way to test that is the spray scrap material that if not the same as the model you are painting, at least is close in texture. Experiment with the ratio's and note what the ratio you find works best. I also will add that before spraying a model, spray the paint thinned the way you noted on a piece of scrap and see if it looks good, sometimes paints change their formula and what worked may not, not to mention that room conditions might affect it, too.
It sounds a lot worse than it is IME, and really I agree with others the way you really learn is to do it. scrap cars or cars from the scrap bin at train shows can be pretty good mules to play around with or things like the casting sprues from kits and the like you might have laying around.
