I have an aztek 470 and really like it but I would like to start doing more fine line stuff like hand drawn camo and eventually plane camo which is very fine. What brush has the finest line without spending alot and being a substantial upgrade from my aztek.

You can use your standard AB. For soft camo, do it free hand. For hard edges camo, make a stencil/mask the area.

The fine tip for the aztec works for aircraft camo. For hard edge stuff, I mask. I have to play with the pressure settings and paint mix to get good lines.
capnjock

iwata brushes are a good buy I've just got a hp-b on recomendations from users on missing lynx from the test sheet that came with the brush it goes very fine
if you jump over to http://missinglynx.com and look on the reviews/articles
there is a section on airbrushes and also check out ,
http://www.dixieart.com and http://www.bearair.com
hope you find this useful