As well as the above mentioned, in addition to an airbrush, you would also need a compressor and all the other stuff that goes with it, it can be very expensive to get set up.
I would assume that you also ride or race model cars and you want to make these presentable, if this is the case, you would be amazed what you can do with a simple spray can, I'm a member of a model building forum involving all kinds of rc including cars, planes and even long distance lorries, on that forum they have a section called "the spray shop" here I have seen incredible creations using just spray cans.
If you want to do your own car bodies I think this is the way to go, and all the tips and tricks and methods you can find here are the same for either airbrush or can.
Like I mentioned above, a lot of what you do with car bodies involves a lot of masking, I painted one of my planes and spent 3.5 days masking and 15 minutes painting.
In your case it buying expensive equipment would be justified only if you plan to make money from it, or in the case of some of us here your addicted to it
Remember an airbrush is only the tool but spraying is spraying no matter what you do it with, you'll get all the info you need here over masking and stencilling and all the other techniques that you need to know.