Ahoy Hang,
FSM has always been my best source of airbrush information. If you look in the browse-by-subject section on the left hand side of the screen, and look under techniques, you'll find an article from the March 2002 issue by Chris Appoldt titled "ABC's of Airbrushing." This article can be downloaded to a PDF file. Also, from Mar 2001 by Robert Oehler is "Airbrush Aerodynamics". One of the best articles on the subject is from the February 1999 issue by Matthew Usher, "Airbrushing Basics". Look in the index to magazine issues and you'll find several articles by Paul Boyer. Paasche and Badger both have good information at their websites and you can download PDF files of their parts breakdowns.
Hopes this helps.
Tom