The biggest challenge in creating skin is finding the right vertices to connect to the muscles. The skin can do nothing on its own. It needs the muscles to drive it; and without the majority of the muscles connected, it's difficult to judge whether the skin is functioning properly.
The skin needs to be tough. Skin only stretches a little, and it barely compresses. In fact, it's the high resistance to compression that contributes to skin wrinkling. It also has a high bend resistance, enabling it to retain its shape when in motion. These high-resistance values can be difficult to solve. They typically require an increase in the number of substeps used on the solver.
Project: Establishing the Skin
There is no need to simulate all the skin on ...