During LAVOMATRIX, I was in charge of the whole blendshapes thing, including the corrective ones and the facial ones as well. I did a basic list of blendshapes to begin (for example, mouth up/down/small/large etc.), and then did all the combinaison targets to add them to the specific ones, like blowing the cheeks to hold his breath under water, which led to blow the area above and under each lip, or narrow them, etc. I also added some dimples, wrinkles, frowns etc. as our Art Direction was quite realistic. And some other specific ones to allow us to pull his eyelids down and reverse them, for example.
As I was also an animator on the project, it was easier to know what I'll need to create to do each thing written on our boards.
A hand demo with the numerous blendshapes on.