Stable Diffusion is amazing, but I've never seen it reliably generate realistic hands. The examples in the ControlNet repo show a chef in the kitchen with 6 fingers.
Yes you can. Came out a few days ago. Open pose has already support for it. You can not only render realistic hand and feet but also customize the hand gestures. There is a blender plug-in which let's you position your character pose including hand gestures in 3D and then render the needed controlnet masks. It works amazingly well.