I want to put a 2D hat on a video clip of a person, whose head is tilting as he speaks.

I can face-track the face using After Effects CC 2017. I end up with detailed tracking data, which includes face orientation information. I can link the orientation information to a 3D null, but how do I link the positional information of the head? The head appears to only be expressed as a percentage (of what?).

Is there an easy way to connect this percentage data to 3D positional data on a null?

Equally, if I do a simple face track, I get an animated mask. What's the right way to translate one of the points from that mask into a null that could be parented to another object?