The Paasche company recommends correct airflow pressure. The recommended figures are one half to one cubic foot per minute flow, at a pressure of 20 to 45 pounds. Working outside of these limits may result in poor performance of the airbrush.
An airbrush has very delicate internal components. If your air supply has dirt or grit in it, the components will be destroyed. Installing an air filter in the line between the compressor and the brush is of vital importance. An air and moisture filter is cheap insurance to protect your airbrush.
Use water-based paint when you first start out. After use, the airbrush will clean up easily with water instead of solvents. Furthermore, if you goof up, you can always wash off the bad area and start over. This applies to canvas and backer board only, not paper. If your project calls for oil-based paint, immediately clean your brush with paint thinner. Never let the paint dry inside your brush, since cleaning dry paint involves a lot more work and time.
Becoming an accomplished artist with the Paasche airbrush takes time, patience and practice. It is a lot like reading a book on how to play golf--reading helps to a point, but you have to play to become good at it. The key is practice. Have fun with your airbrush and experiment with different techniques.