solid advice here
I can't comment on Aircraft airbrushes and compressors, but it does seem like a good way to start. Also good to see local agent support with a wide range.
If your are near Midrand perhaps go visit them and ask them to demo the equipment.
http://www.aircraftair.com/index.php?route=information/contactJust to add on to what has already been said you need to get a good double action gravity feed airbrush and a compressor with a tank. Its a two part system, the two have to compliment each other otherwise it will be a frustrating experience. A balanced approach is required.