You will blend between two caches. See below:
An alembic cache of your skinClustered character. This is the one with the final hands/feet/face (and tail if you character has one) This is the product of the same rig the animator used to animate the shot, and that rig also had the skeleton geometry in it, that you passed to the muscles. So you need an alembic cache of this deformed skin, as this is what you'll blend to later. Let's call this skin_animated.
An alembic cache of your skin simulation. Typically this is the simulation of the body. We don't simulate the hands/head/feet etc. (there's no reason you can't, but let's keep it simple) Let's call this skin_simulated.
Right, so start with an empty Maya scene.
So now you should see, on the first frame of the shot, your two caches sitting on top of each other. They should both be at bind pose, at the origin.
Duplicate skin_animated, call it skin_wrapped
Create a wrap deformer between skin_simulated, and skin_wrapped, so that skin_wrapped is bound to skin_simulated. Don't forget to turn exclusive bind ON so that it's fast.
If you scrub the timeline now, you'll see that skin_wrapped looks noisy in the hands/feet/head, that's fine, ignore it.
Select skin_wrapped, then select skin_animated
Create a blendShape
Set the target weight of skin_wrapped to 1
Hide everything except skin_animated.
Right click on skin_animated and select Paint > blendShape1
Paint a value of 0 to the hands, feet and head.
Smooth the weights so the transition isn't so harsh.
That's it! It's a duplicate of your original skin and 2 standard Maya deformers 🙂
bro please make a dedicated video for this workflow please....!