Furring a moveable jaw

So I have another question. How exactly is the best way to fur a movable jaw? You have to make it two pieces right, one for the jaw and another for the rest of the head? But then how do you get them to look like they're all one piece? Or if it's one piece, how do you keep it from being wrinkling?
Does anyone know of any tutorials that go over this or some advice?

Thanks so much.