Strange airbrush problem with Artrage 2.5

I was pretty happy with Artrage 2.5 except the Airbrush feature. Somehow it didn't work with the stylus pressing on the screen, but worked when I press the mouse button. So I have to leave the stylus slightly in the air and press the mouse button. The feeling is actually pretty for it really feels like I am airbrushing something. Maybe that's the intent (I haven't read the manual yet and probably never will :-E ).