Single action means the trigger moves in one direction (usually up/down) and controls only the air flow.

Double action means the trigger moves in two directions (up/down, forward/backward) and controls air flow and paint flow.

Single action air brushes control paint flow by adjusting the needle via a threaded mechanism. It is not practical to change the needle position while spraying. Double action air brushes allow you to move the fluid needle with the trigger while spraying.

Double action allows you greater control over the spray mist because you can change the air flow and/or paint flow with the trigger while spraying. Although this controlling two things at once requires more experience to do well. A single action air brush is easier to operate since you are controlling only one variable - air flow, but does not offer the spray mist control of a double action.

There is no special paint for air brushes. They spray any paint so long as the viscosity (runniness) is low enough. Additional thinning of the paint is often required due to the very small fluid nozzle used on air brushes.

Check around.  There are a variety of tip and needle sizes available that are useful with different paints.  I found mine at an art store years ago.  I ended up with a fine and medium sizes for different paints.  No, I don't remember which was for what paint.  I think that Floquil and some others used the fine point and Polly Scale sprayed better with the medium point, but check yourself to be sure.

Also, I found I could change the paint flow on my single action brush as needed by spraying on scrap material to get the right flow then on the model without really stopping.  I'd do that with a dual action anyway.

Terry

Hi Andrew,

For years, I used a Badger setup that included a diaphragm compressor, combination moisture trap/regulator and Badger Crescendo double action.  I also had a Passche VL, but prefer the Badger.  The only problem is that the compressor ran constantly.  The moisture trap was just large enough to prevent air pulsing and back pressure was relieved by a small hole in the adapter fitting between the compressor and airhose. Maximum flow pressure was about 25 psi.

I bought an inexpensive compressor/air tank from Harbor freight.  Unfortunately, its pressure switch allows it to build up 125 psi, but switches on at 90 psi.  I cannot find a a lower pressure cutoff switch, so I wind up pumping the tank to maximum, shutting it off, keep an eye on the tank pressure and flow pressure.  The tank holds enough air to brush an On3 boxcar.  NOT the ideal set up and the compressor is LOUD!

There are newer hobby type compressors that are relatively quiet when running constantly and ones that are a compressor/tank/regulator combination.  The tank also acts as a moisture trap, but use a small trap/regulator between the output and the airbrush feed hose If you buy a large compressor, make sure that it is the OIL LESS type and

I would recommend that you not go cheap and expect to pay about $200+ for a good setup.  A cheap setup will be frustrating to use and yield poor results and you'll only wind up buying a good system to replace it. Like any other tool, buy the right one that will do the job right the first time.

Hope that this helps.

riograndehombre

I bought an inexpensive compressor/air tank from Harbor freight.  Unfortunately, its pressure switch allows it to build up 125 psi, but switches on at 90 psi.  I cannot find a a lower pressure cutoff switch, so I wind up pumping the tank to maximum, shutting it off, keep an eye on the tank pressure and flow pressure.

I just took a look at my cheap-o compressor.  The pressure switch is somewhere inside the motor case, so I have no idea whether or not it is serviceable.  However, the system that I built out of parts uses a common pressure switch from a hardware store, and those ARE adjustable for both the high and low pressure.

I cannot think of any reason that you could not wire the compressor through a secondary switch set to a lower pressure.  The built-in switch would serve as a back-up, but would normally never operate.  You could even install a simple bypass so that you could run the compressor at full pressure for larger jobs if needed.

On the other hand, what's wrong with letting the thing run at full pressure, other than making a little more noise?

Re:

I bought an inexpensive compressor/air tank from Harbor freight.  Unfortunately, its pressure switch allows it to build up 125 psi, but switches on at 90 psi.  I cannot find a a lower pressure cutoff switch, so I wind up pumping the tank to maximum, shutting it off, keep an eye on the tank pressure and flow pressure.

I bought a regulator from Harbor Freight, and a few fittings from my local hardware store, and hook the rig up to my shop size air compressor that puts out 100+ psi.  I can throttle the air down accurately as needed.