I'm using the glass approach for this first project (4 panes of glass), and I just did a test run of how to make some fog appear. So, with some help from Abby,I put the top pane of glass in the freezer, which created the fog appearance, but you need to blow on it to make it really show up. My next approach is going to be using a hair dryer on it once it comes out of the freezer to make it appear a little more quickly and easily. Just a little trick I thought I'd share because I probably wouldn't have thought of it had Abby not have suggested it.
By googling I also realized that the California Raisins commercials of the past were all claymation. I always liked those guys, so here's a link to one of their commercials just for fun.