Timeline beginner question

Hi so I have a character animating with mecanim (kind complex state machine). & I have a blend shape facial animation that I want to try to overlay using timeline.
The head movements are ok so I have configured my mask with head green, rest of body red.

But I'm not sure how to set it up in Timeline?

I've tried a few drag drop attempts but am not able to seperate the existing base character movement from the layer I want to apply which is head movement and blendshape animation.

Whats happening is my base animation (standing) is being full body overridden by my facial animation file (sitting) so instead of seeing a standing talking character I see a sitting one- that has frozen body animation and moving head like I do want to see.

Any ideas? I can't seem to get the override animation workflow.
What should be in each slot of timeline to make this setup work?

Thanks

 

Do I need to have the characters state machine in timeline before I can add an override layer and put the facial animations on top?