Not sure what your solution is, did you break the mesh up and each finger is a separate object? Well anyway, assuming you made each "part" into a separate object, you can add a Corona Compositing Tag to each part. The one part that will render, leave all the options ON. All the other parts, turn OFF Seen By Camera. This way, and shadows should still appear on each part as if it was whole. You just need to have those settings change so you can render each part. Hope that makes sense.