I've never used an airbrush, although I do have one and a full set of colors for it. My question is this: If I'm doing something big like a building that will be all one color, should I go ahead and just color my icing, or should I ice the whole cake in white bc then airbrush it with my beige color? Will the white show through?

I specifically got my airbrush to do dark colors such as red, royal blue and black. In reality, I've found that the coverage isn't smooth enough to suit me, so I don't use it on large things. But, you might have a better touch than I do. It's hard to get enough color on...without causing runs and splotches. I think the key is many thin layers, but so far I just haven't found the right combination. I've also read that thinning the color with everclear or vodka helps - you can lay down more color without fear of making a runny mess, due to the higher evaporation rate. Haven't tried that yet.

I'd definitely practice on a dummy first. And definitely on icing. People recommend paper towel for practice, but the two substances behave totally differently, IMHO.

On the other hand, if you're looking for a kind of organic look that isn't totally smooth and one color all over....the airbrush might give you exactly what you're looking for.

I had the best luck so far spraying white on a sugar mold (it just wasn't pure white enugh to suit me). And gold on fondant. That worked out GREAT!

I've done several red, black or navy cakes... (lots in my gallery!) I always colour my icing first to a lighter shade (i.e. a darker pink if I'm after red). Also, if I'm after black icing, I always sart with chocolate & airbrush that with the black!