@Casey H.: I have a Grex Tritium with .7mm needle. It is a very good airbrush, but as I wrote earlier in this thread, I can't get it to do more than one mold, maybe two, before reheating is required. Again this depends somewhat on the temp of the spraying room. But the Grex does NOT do splatter. If you go back several pages in this thread, you can read about my experiences. The confusion arises from the fact that the Grex does splatter paint, but it will not do so with cocoa butter. The tech support people confirmed this experience of mine and suggested splattering off a spatula. I also tried a Badger and a Paasche; neither does splatter. Maybe there are airbrushes that do, but I don't know.
I have never sprayed luster dust (and don't think I would run the risk, but that's your decision). Grex says a 1HP (minimum) compressor is required for a .7mm needle. If, however, you think you might ever switch to an HVLP gun, I would go higher because my 1HP struggled with an inexpensive HVLP paint gun and a 2HP does not cost that much more than a 1 [correction: I have a 2HP, and it struggled with an HVLP gun--it was fine for the Grex .7mm; I think some HVLP guns require higher PSI than 2HP provides.]
My production sounds somewhat similar to yours. I found that switching from a Paasche to a Grex was a huge improvement, but I have to say that the Grex still requires frequent reheating. It got so frustrating for me that I more or less gave up on it. It is still great for gradients, which are difficult (though not impossible) with a higher-power HVLP gun.
