I airbrush Tamiya (Tamy) paints mostly. When I get the small 10 ml bottles, I fill almost to the top with the tamiya thinner (other modelers use isoprophyl alcohol) therefore, the bottle is ready for airbrushing. So far this ratio (like 1:3 thinner to color) has worked fine for me. Read it on-line once and used it and worked, why change it. I also use between 15 to 20 psi in my air compressor. Use Tamy thinner too because I find that it has some additives (the the isoprpphyl alcohol doesn't) that help the gloss in Tamy colors. But let me tell you, even the spray cans work well. Specially the clear coats out of the spray can are luster than if you airbrush. The only thing with spray cans is that you have to give several thin coats to get the final coverage. That has been my experience.
