Nurnie Facial Rig
Maya - Sculpting and Rigging
For each facial blend shape, I sculpted several in-between poses so that the non-linear progression of the blend shape would appear more natural. The controllers drive set driven keys which activate multiple poses at a time to arrive at the final shape. I found it most efficient to work on a single side of the face, and then wrap the shape to the other side in order to maintain the correct vert order (I was working on Maya 2014 at the time).
The Nurnie model was provided courtesy of DAVE School.