For Dual-Action Airbrushes: Using finger for control, push down on the trigger for air flow. With trigger pushed down, pull back to release paint flow. For finer lines, turn the air compressor pressure down, get close to paint surface then push down and pull back on trigger just a little.
Reassemble airbrushes: Use airbrush spanner to screw the nozzle back onto the airbrush. Make sure nozzle is snug. Do not over tighten. Hand tighten the nozzle cap and needle.