Talk to me about airbrushes

[Bowman]

Piston type; oil-less compressor (it says that, and not diaphragm compressor - whats the difference?)..............working pressure is 0-4 bar (up to 57psi) - so I assume the pressure output can be adjusted to whatever I need?

My apologies. The amazon description said diaphragm. You want piston compression, just like a car engine. 

I'm not sure how the pressure is regulated. The user manual doesn't explain that well. The maximum pressure available is 57 psi. Once you start spraying the pressure drops to the effective pressure (most likely around 30psi). I'd assume there is a bleed valve at the bottom of the water trap. That way you bleed off more air to drop the psi even more.

[Bowman]

Is it possible to get a smaller nozzle for the patriot, or is it only made for a .75 nozzle?

Also, what is the difference between the nozzle size and the needle tip size?  Or is it the same thing?

A quick Google search shows that the Patriot 105 can come in a "fine" tip also. This is a .5mm nozzle. Buy this, not the .75 tip.

The tip depends on the opening of the nozzle and the narrowness of the needle. So a smaller nozzle requires a finer needle. The needle obscures the opening of the nozzle when in closed position. Pulling back on the trigger pulls the needle back, creating a small opening where the paint comes out. The more the trigger is pulled back the more the needle recedes from the nozzle, the more paint comes out.

Hope that makes sense.

[Bowman]

Do the good people of LAF bother with moisture traps?

Yes! A tank will collect water, but you do want a drainable moisture chamber between the compressor and airbrush. Water contamination in the brush will make splotchy painting.

If you look at the link Timbor gave for the Badger compressor, you'll see the moisture trap chamber.