How does one go about airbrushing a cake?
Is there a special airbrush/food coloring that needs to be used for this?

Yes, besides needing to have the airbrush itself, there are special colors for use in airbrushes. I don't know quite what the difference is, but I just invested in an airbrush and a whole bunch of colors. I haven't had a chance to try it out yet, but I'm hoping to soon. The airbrush comes with a manual on how to use it and there are some really good videos that you can look up on the internet to help you get started.

There are specific airbrush colors made.The colors are the consistency of water but of course for the airbrush.You don't dilute them either..Americolor,Chefmaster,Lucks etc all put out their own line of airbrush colors.

You don't need a special airbrush just one that hasn't been used for anything else but it is worthwhile getting airbrush food colours they reduce the chance of clogging and will give good coverage. I expect those with more experience can give you the low down.

Yours aye
Puss