I did a lot of air brush illustration when I was freelancing full time. I used a smaller, finer needle I imagine than what you'll be using, but the principal's the same. Since you're using an air compressor, you'll need to trap the moisture that naturally occurs in air. Otherwise, when you least want it, you'll get a blob of water mess up your work. I didn't use a compressor. Instead, I bought a couple of beverage tanks and had them filled with CO2. It has no moisture in it, and because it's compressed, lasted for many hours of solid airbrush work. I have a two-stage regulator -one gauge shows how much air I have and the other shows psi. For my work, I preferred 26 psi. Heavier paints require more pressure; inks require less. I worked in guache, which is an opaque watercolor - heavier than regular watercolor, but lighter than acrylics.
The number one rule for airbrushing is this: CLEAN IT WHEN YOU'RE FINISHED. If you let paint of any type dry on your needle, you're screwed.
Good luck and have fun. - Roberta