I'm not sure I understand well your question, so pardon me if I'm off target. For the figure to be posable, you have to have the Geometry divided into as many groups as there are body parts. Hence, you have to have a rThumb1, rThumb2 and rThumb3. For the materials, you can divide your geometry just as you want, and you can keep a group composed of polygons belonging to both hands and called "glove" or "thumb". The borders don't even have to match the bodyparts borders. Just don't give a material group the same name that you gave to a bodypart group. And never use spaces into groups' names. And never ever feed them after midnight. (ah well, forget this one..)