Hey Gang.
A lot of the guys here have said it correctly. It's just practice, practice, practice.
Now, as for a starter airbrush. I came across one due to an article in an airbrushing magazine by an airbrush artist in my town. It is a double action airbrush that can do pencil thin lines to a variety of wide spray. Not large areas but perfect for the modeler. It can be found at your local or online Harbor Freight Store. It is the Central Pnumatic Deluxe Airbrush kit. It has both syphin and gravity feed. In the magazine article, it was said to be designed off of the Iwata. It cost only $15 USD. I got one of these airbrushes and love it with the detail work I can do with it. From models to doing motorcycle parts. I know, I know, some will say it is too good to be true. What I can do is reference the magazine article and page if you don't beleive me. The artist that wrote the article (Chris MacMahn of Aero Grafix) also uses it for his line of work. He uses all kinds of airbrushes from Pasche, Iwata, etc. I know we are all feeling the economic pinch. I promise, that this will not only fit your buget, but you will be more than happy with the results.
If you have any questions, feel free to drop me an email. johneagle777@yahoo.com
Cheers
John (Ohio, USA)