And here is the second. Sorry this took so long! Day job, and all that.
What I'm going for now is a standardized way of creating corrective Shape Keys, rather than a hodgepodge of Blender techniques.
My approach is: careful location of loop cuts in the areas of greatest motion; careful weight painting and rigging to handle those areas; Shape Keys only as trivial fix-its and not big repairs for mesh distortions. To that end, I use Proportional Editing (with a very small area of control, done with Alt -), Grow Shrink Along Normals, and Grab, Rotate only on one constrained axis.
https://youtu.be/OXxMzyL_g40
Okay, coming in on the home stretch!
Here is an example of Chatanyara Kusanku, using an Alpha 5.1 mesh:
https://www.youtube.com/watch?v=CU7w2JzQTTQ