One other question for you Paul. What type of air compressor are you using? Is it an oil-lube or oil-free type? If it's an oil-lubed compressor, oil might be carrying over and slugging your airbrush. Change the filter element on your filter/regulator. You can also buy a desiccant snake air dryer by DeVilbiss through Eastwood Co. for $20. You'll really want to put it in-line after a filter, but before a regulator/filter because they have a high pressure drop so you feed it 90psi, then use the second regulator to drop the pressure down to 35-50psi (or whatever your paint recommends). The desiccant snake will definitely improve your air going through your airbrush.
I have a large 60gallon 3HP oil-lubed setup for my garage. After my tank I have a course (50 micron) filter, then I have a 10 micron filter/regulator and a quick connect fitting. When I run my airbrush, I have a quick-connect fitting on the end of the desiccant snake and the other end is fitted to a moisture indicator and another mini filter/regulator that feeds my airbrush. This way I'm only drying the air to my airbrush and I can still use my compressor for other tools without burning through the desiccant snake.
Of course, all of the air prep is worthless if you don't keep the airbrush clean...