Applying Face Tracking Data to masks

Try this:

1. Face track your shot
2. Set the original mask to None
3. Select the pen tool and set it to Rotobezier
4. Add a mask to the face starting on the left corner of the mouth, then the top, then right, then bottom, and close the mask.
5. Open Window/Create Nulls From Paths
6. Select the new Mouth mask path and choose Points Follow Nulls
7. Select the four nulls that were created and press 'p' to reveal the position property
8. Select the Footage layer and type Mouth in the search timeline field to reveal the Mouth data
9. Make sure that the Links/Columns column is open in the timeline by pressing Shift + F4
10. Use the links pickwhip  for each null to attach the appropriate corner to the appropriate data
11. Expand the mask as necessary
12. Adjust the tension on the mask points if needed by temporarily turning off the expression the script applied to the mouth mask.

There you go. 

You may want to use the more generalized mask tracker instead of the face tracker. That kind of is the whole point. Draw a mask around the mouth and let it do its thing.

Mylenium