It is bound to the A key. Finally, it will allow you set the glue and transparency for the paint. Please see the layers section of the page for more information about glue and transparency. Shift -dragging constrains airbrushing to vertical and horizontal only. Command temporarily activates the path arrow.
Option temporarily activates the eyedropper.
The airbrush is almost synonymous with photo-retouching. It's better than Noxzema. Central to its functionality is its gradual effect. By lightly clicking, you can subtly add paint. The klutzier you are, the lower you should set your pressure, and the more forgiving the airbrush will be.