How a double action airbrush works explains in easy to understand exactly ho easy it is to use a double action airbrush.
With a double action airbrush you press gently down on the trigger for air and pul back on the trigger to start painting flowing. You always have the trigger fully depressed and adjust the amount of air flow or PSI via the compressor/regulator not by feathering the trigger.
Pictured below Cody is gently pushing down on the trigger of the airbrush. At this point you should only have only air coming out of your airbrush. Get in the habit now of always leaving the air on while airbrushing, even between strokes or applying paint.
Summary: The amount of air or PSI as it’s often referred to should be regulated at your compressor not the airbrush trigger; you always want your index finger to depress the trigger fully downward.
Pictured below you can see Cody is not only pushing down on the trigger but has also pulled the trigger back, at this point you should have not only air but paint coming out of your airbrush. The further you pull back on the trigger the more paint will flow. In other words the further you pull back on the trigger the more paint you will be spraying.
Again with a double action airbrush the further you pull the trigger back the more paint you will apply. So the amount of paint you spray with a double action airbrush is regulated by how far you pull the trigger back, the further back the trigger travels the more paint will be applied.
Summary: With a double action airbrush pushing down on trigger gives you air, pulling back on the trigger gives you paint, do both you get both air and paint. While airbrushing always leave the air on (trigger fully depressed); air always on.