I decided to make individual controls for the eyebrows, as I want flexibility, and I'm not sure of all the facial expressions I will need. I followed the Pipeline 1 tutorial for the brow movement, but mostly used a similar setup to the lateral mouth movement. It seems to be working and I have tried out making a few of the expressions from my expression sheet.
There is a problem with the central control on the upper lip. When I click off of the keyframes I make for this control, that part of the lip appears to move back to its original position. It hasn't actually moved back and I think this is just a problem in the viewport, as it renders fine. I'm not sure how to fix this, but I would like to. I want to be able to see how I'm posing my character for animation.
This is what happens in the viewport when I move one frame over. There is a similar issue with the some parts of the brow, but again, it renders fine.
This is a render of the same frame as the above screenshot.
Aside from this, the rig seems to be working. Next I will make sticky eyes and attach the eyelashes.