i've been trying to figure out which gun he uses usually, with the cup underneath...it seems to spray so evenly. i have a kopycake airmaster, and i absolutely hate it!!! i bought a lady out of her business, so it was her choice originally, but i think she'd screwed up the needle, because it sprays air before i even have the trigger pulled. it also just has that tiny little cup on the top, so if i barely jiggle it or turn my hand, big drips of color end up on my cake!!! grrrrrrr!!!!!!!!!!
i saw a post on here about a preval, but not sure if he also uses another one or not.
Your kopykake brush is single action so the air is always flowing through the brush, you can only control that by turning the switch on the compressor. and to prevent spilling the colour that sits in the cup, onlyput a few drops in, i never fill mine to the top. sorry i cant help with what Duff uses.
Also you can purchase other airbrush pins for you machine and still youse your KopyKake compressor. The kind with the bottle on the bottom are called Siphon airbrushs. the only problem with those are you have to use SOOOO much color to fill that bottle, but some people love them. You can buy pens with bigger cups, KopyKake sells one that has a bigger cup on the top.