I've used ShapeBlends for making the vowels and constanants.
The most used for these were:
"Left and right Pout" lips,
"Open the mouth" and "forward and Backward" for the Jaw,
plus "Blinking" the eyelids.
I'll have to try doing somw facial shapeBlends on another model.
I have tried a mental Ray render with a displacement map on it
but it doesn't justify the render time, so I've used a bump instead.