Very cool. Really fascinated by your process. A couple of questions on your sculpting process.
I assume you start with a low-res mesh. Do you bake back to that original mesh after sculpting or do you re-topologize a new low-res mesh based on where your sculpting takes you?
If you re-use the original low-res mesh, do you make sure that sculpting is only ever subtractive (so that it remains within the original low-res cage) or do you also add height as well - say with a clay brush?
I would assume to work quickly that you try to bake back down to your original mesh as much as possible and therefore keep sculpting limited to more surface details.