Be nice; this is my first video tutorial! I will update the description as I think of other relevant details and to answer some common questions. (The audio is being updated also; patience please!)
The two cakes in the video include a quarter sheet cake in pink, orange, yellow, green, blue, and violet; and an eighth sheet cake in yellow, green, blue, and violet. The quarter sheet is iced in Bettercreme (a whipped topping type icing), and the eighth sheet is iced in buttercream (palm oil shortening base). I recommended a freshly iced cake because a cake with dry icing will not comb smoothly.
This effect can be achieved with just two colors, although I recommend complementary colors, as not all overspray can be prevented.
The airbrush I use is a Bakery Crafts brand, set at 10 psi. The airbrush colors I use are a combination of Bakery Crafts and DecoPac brand colors. And yes, I hold the airbrush weirdly because my index finger locks up; so I pull the trigger with my thumb, and have done so for ... 13 years now.
The icing comb and turntable are nothing special, and can be found in any craft store that has cake decorating supplies.
No, I am not the first to make this design. In fact, I learned this waaay back in 2002, when I started training how to decorate!
http://www.bakerycrafts.com
http://www.decopac.com