As a food network groupie, I have to say that I think the materials used for painting with chocolate is pure cocoa butter, not white chocolate or bark -- which would be way too thick. I am not exactly sure where you get pure cocoa butter, but I'm guessing it's not at Walmart.

Also, you should know that working with chocolate is one of the most difficult mediums to work with -- just a little moisture and chocolate will seize up on you, heat it too hot and it remains soft and won't reset. Again, not sure about the cocoa butter. The stuff you buy at Walmart for dipping pretzels and the like has additives to make this problem less likely, but again, is probably too thick to paint.

Lisa