Ok, so this may be a stupid question but Ive seen a few things about airbrushing dust and such on finished cakes.  can anyone tell me how to do this? do I need to water down the dust? is there a certain size needle needed for this? Thanks so much!

 I use to use the dust mixed with vodka, Shake the cup really good. Be sure to clean the cup very, very good after doing this. But now. with so many sheen airbrush colors, that is what i use  , not the dust. pure lemon extract with the dust also can be used , but i just alway use vodka(use to) not now. hth