head scene example https://www.youtube.com/watch?v=-5nOF4Rm8EA
head-body scene example https://www.youtube.com/watch?v=Ghh6zMHAEmA
-you can adapt the target curves to new targetHead , or create your own curves , use make live option to can draw curves on the surface
need be careful first point of each curve in the same place of the source curves to do not have reversed curves issues.
-besides the clusters moving the mask low poly head , you can move the vertex freely just to cover targetHead better.
-tricky parts are between lips , maybe you will need smooth that area and re model or use other metahead to catch that part using a blendshape
dont make fun of my mel scripts :) im not a programmer