Just bought a Paasche VL double-action airbrush, which is a fabulous inprovement over my former simple Paasche single-action, but it has a tiny knurled control, a lateral wheel-like thing, just forward of the push/pull air-control button. Damned if I can figure out its function from turning it back and forth, and there's nothing about it in the printed material that accompanied the brush.
What is its function, and how do you use it?
Stephan