1. How to set up
Blend Shape

Blend Shape is a common facial rigging.
1.

First, duplicate the neutral head. In this example, I will make two
shapes so I duplicated twice.
2.

Sculpt the models just you duplicated. They are the
target shapes.
3.

Select
target shapes first, then select neutral_head.
Apply Blend Shape. Create
Deformers > Blend Shape
4.

To see
the control slider, Window
> Animation Editors > Blend Shape
5.

Move the sliders and see the expression.

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