He mentioned that there are 3 grades of hardness with this synthetic wood that he uses. He uses the softer grade for large shapes that aren't detailed, and the harder grade for very detailed parts (like the face of a character). He used medium grade when sculpting the pig.
cool interview thanks for posting it! I really love mirocks take on the RxH sculpts, now i just have to get my hands on some of them =]
Renshape comes in different forms. For model builders, it would be a block and they would sand, cut, carve it to what they needed. It was also called red-stuff and took paint a lot better because it wasn't so porous like wood and had no grain to it. That synthetic wood that he is using is probably similar.