Okay, slight necro here, but it's a good thread. I just tried this technique with with mud (2 bondo/1 resin) and the foamies stuck to the mud like crazy and left behind little pieces that I had to razor off. Is there some way to keep the filler from sticking to the foamies that I don't know about, or do I just need to use pure Bondo with no resin?
My mistakes aside, this is a great technique.