Hi,
I'd recommend the Iwata Revolution series (gravity feed) brushes as an excellent introductory brush. I can achieve quite fine lines, even though the nozzle is .5mm. Equally, you are right when you say that you need a compressor that will give you around 10 -20 psi. An adjustable compressor with water trap should stand you in good stead. The Iwata line of compressors is also very good. Go to Dixie Art (
Dixie Art & Airbrush Supplies Home Page: Airbrush and art supplies, I think) for a very good selection of brushes and compressors with quite competitive prices. I use Iwata equipment, and I'm very happy with my results. Good luck with your search.
Other forumites, please chime in!