Here's a quick link on the type of paint we used.

It was very important that it was easy to use and non-toxic so any child in any situation could be a part of it. It's called gallery glass. Make sure it drys fully before touching or moving. Kids like to pile it on and if not dried fully it can run or impressions can be left into it. We also spray coated it after it dried for extra protection. Also it works best on surfaces that are sandblasted.

http://shop.hobbylobby.com/crafts/gl...gallery-glass/

Josh