Gelato - this is a riot! I'll bet your students loved you for letting them paint on your car. :-)
When teaching el art, I had a lot of stinky old tempera. I turned my 3rd graders loose on my kids beater. Only restrictions were the saftey stuff, like windows and mirrors. They had to make a design that was compatible with teir neighbor's little section of the vehicleIt was a gas! My children were thoroughly embarassed as I drove it till the rain washed it off. By thet time my teenagers had completely disowned me......Ah yesssssssss, Payback is so rewarding sometimes.