PSI Question

The recommended pressure setting should be in your airbrush owner's manual. It is different for different airbrushes and also depends on the type of paint your use.

Typical airbrush compressor gauge varies 1-3 psi between static and pulling trigger reading. But poor compressor vaires much more.

Start with 15 psi if yours is a gravity feed, or 20 psi with a syphon feed. Adjust the pressue until you get a fine misty spray from the airbrush with little or no overspray.

What airbrush do you get anyway?

It is not real critical and depends a bit on the thinning ratio.  I run about 15 for gloss, 20 for flats.  Too high a pressure tends to make paint dry on the way to model surface, giving a rougher finish. Maybe not too objectionable on flats, bad for gloss.

Some folks say there is an atomization problem with pressures that low- I have never had a problem with atomization.