We used clear Inkjet Waterslide Decal Paper with a couple of coats of Rust-Oleum Crystal clear enamel after they were applied. It's a little tricky to work with, but once we figured it out, they came out really nice.
Great movie. The decal turned out really nice for that. I didn't have as much luck using the Testers white waterslide version. I had a lot darker colors though.