I thought I'd document how I do lip sync using the face nulls.....as opposed to the dope sheet way. The dope sheet is great for doing it really quickly, but I believe you can get better results using the nulls almost as fast. Usually you have to clean up the dope sheet anyway.
So, here's how I personally perfer to do it:
1) The two main nulls are the Sync Null and Lips Null. I first use the left/right arrow keys to move these at Frame 0 to make a keyframe. So, essentially they are at the default location.
2) Now I select both these nulls and press the icon marked in green to keep their keys in the timeline.
3) I copy both Frame 0 keys of each null. Then I scrub through the dialog and paste new keys at the points I think will need a new mouth shape.
4) With all these keys in place, I'm always working from the mouth in the default position at each new mouth shape. I find it easier than going from different shapes every time.
5) Now I just work my way though each set of keys and make the relevant shapes. Invariably, I can copy similar shapes in the earlier parts and paste them in the latter parts.
6) Once the timing and shapes look right, I can then add some variance to the mouth shapes such as a wider mouth for one A sound or move the jaw from side to side with the jaw null.
Good Luck!
