BTW, sorry no one else has answered this. I use different things for different purposes - AmeriColor or Chefmaster airbrush colors for airbrushing/stenciling parts of cookies (turns out extended powders like Crystal Colors, which is also food-grade) works well in the gun too; PME luster spray for getting quick/broad/thick coverage very fast and evenly over entire cookies (it can't be beat for this purpose, though it is very expensive); and usually an extended luster or highlighter dust (like Rolkem, though there are other highlighter brands) for sponging and painting accents. While Rolkem and other highlighter dusts offer great/thick coverage and are VERY shiny, the downside is they are not approved for food-use in the USA. All highlighters (that I've seen anyway) are labelled "nontoxic" or "for decorative use only". But some metallic luster dusts are food-grade and cover pretty well. I also sponge and paint with PME luster spray (sprayed into a container and then applied with a paint brush), as it goes down super smoothly with no clumping. But it evaporates really fast too, which can be a plus and a minus.
Sorry, I didn't have a more direct answer - but I do use different forms depending on the application and effect I want.