I have found that with really complex concepts like those being presented here, an intensely methodical approach is called for. So - realizing I'm re-inventing DigitalDreamer's wheel - I've gone through this entire thread to this point and copied the key concepts into a ODT document (I do all my online stuff in Linux, and OO.org is installed so...). Now, by key concepts I mean key concepts to me - no one else might find them relevant. Still, anyone want it, I'm happy to share.

So, printing it out - oh, the trees, the horror!! - 70 pages later, I think I'm beginning to grasp what I want to be doing.

Firing up the GIMP - yep, I'm poor and proud of it! - I am first creating a lip mask as suggested by BagginsBill, with borders that extend slightly beyond those of the lips themselves. Kind of a fuzzy border, in order to blend properly. Something my mum always cautioned me about: blend, blend, blend! Now, I don't wear foundation much anymore - a bit hard on the skin, most of them - but the concept stuck.

This is stage one. I'll post the results and go on to stage two. I did have to delete the VSS_01 prop when I ran that material file - suddenly, I had two VSS scripts.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks