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The most important thing is "double action"! Meaning you can control air flow from nothing to maximum, as well as paint flow from nothing to maximum.
I totally agree with the above. An airbrush is a precision instrument, not a lump hammer, and needs to be treated as such.
You'll find that for every minute of actually spraying, you should be spending between fifteen and thirty minutes cleaning!
A bit of an exageration, but not far off the mark! The 'brush will need to be blown through with thinners immediately after use, and then thoroughly cleaned around the nozzle, jet, chamber and especially the bottom and feed tube (if any) of the paint cup or bowl. NEVER use hard materials to clean, such as wire etc, and check with the supplier for suggested cleaning materials such as a foam cleaner etc.
Even allowing the 'brush to stand for half an hour with paint still in it will cause stoppages, and much quicker with acxrylic paints or varnishes, which set into a 'plastic' type of coating, which can ruin a 'brush and mean replacing needle, jets etc.
Glenn mine there are 9 different nozzles, the airbrush comes with 6 and the other three you have to buy if you want them. You can control paint flow by rotating a 'cylinder' shaped piece towards the back of the airbrush. It's gravity and siphon feed. I have a Badger aswell... not as easy to clean but still a great brush.
The Aztek sure wasn't cheap. It was 120 dollars so I asked for it for my birthday....