BTW, what's a good place to get relatively small quantities of EVA foam sheet cheaply?
I've been vacuum-forming Foamies from the craft store, but it only comes in limited thicknesses (2mm, 3mm, and 6mm) and sizes. (I can only find the 6mm in 9x12 sheets, which are way too small. I can find the 12 mm stuff as 2x2 floor mat tiles, but that's a bit too thick for my purposes.) Do they make 4mm? I'm guessing so, since EVA is used for so many things, but I haven't figured out where to find it.
EVA foam can be useful if you want a little loss of detail, e.g., to smooth out a shape as an intermediate step in making a buck. (I hate sanding.) Of course, the detail is much better on the inside, and I'm thinking of using it for making flexible molds cheaply.
I will second the idea that you want to be careful about scorching the stuff, and that it varies by make and model. Just among seemingly identical craft foams, Foamies brand cooks up (and scorches) faster than the off-brand stuff from Hobby Lobby, which I like better.