Okay, did this today. For those of you reading my story in the OffTopic:Chipmunk, today I brought a high school kid and his friend in. He's been saying he wants to learn new things and recently showed me his tie dye cake which were from boxed mixes:
Well, that wouldn't do, now would it. So I said, let's make it from scratch and cooler! He was very excited. So he and a friend came in. He was more interested in the finish so I prepped the cake. We did Pierre Herme's cocoa cake (3 layers), brushed with caramel sauce, alternating layers of peanut butter curd and caramel ganache (his chosen flavors), and encased in a chocolate mousse. The cakes were then frozen to prepare the cake for the glaze. We prepared the bright colors according to Drewman's recipe above. We each picked a color - turned out to be the primaries sort of.
Then I had the kids stir to cool down the base glaze which they colored black...cuz that's what kids do to perfectly good pastries.
Yes, i fed them my chocolate chip cookie dough so they could be a professional chef like me and eat like I eat!
I had made 4 individual cakes.
And then we poured the black glaze kinda heavy like in the videos. The kids then drizzled the colors. I said "less is more" and they clearly have a different understanding of that phrase 
I didn't remember the airbrush so I tried blasting with alternating blow torch and freeze spray but that didn't really work. But, a mirror glaze is still a mirror glaze. The kids were ecstatic and couldn't wait to take them into work at Sonic to show everyone what they had made. We're set for another date to re-do it using LESS color and the airbrush.
