Thank you! I used a trick i learned from Andrew Kramer ( www.videocopilot.net ) many years ago. He explains how to do it in a tutorial called "demon face warp". Basically you use the motion tracker in after effects to stabilize the face of your subject. Then you precompose that footage, and use an expression to remove the visual effects of the stabilization. This somehow makes the "liquify" filter stick to the tracking data so that it follows along with the facial features.