P2Design presents a tutorial on skin deformation using 'driven normal maps.
So here is my advanced tutorial on skin and muscle deformation. It is based on my Orkish warrior character that is still WIP. I encourage you to follow this thread if you're interested.
This is an advanced tutorial, I'm dealing with complex skills with node editing, rigging and drivers so If you're a total beginner or don't feel comfortable with these, you may watch the following tutorials first: