This recipe has a few key elements that make it work:

• Blend Shapes: You need to export the Blend Shapes from your 3D package. Blend Shapes store different version of the same mesh. The mesh has to have the same number of vertices. When creating new Blend Shapes, you can only move the vertices around (you cannot add or delete vertices).
• FaceAnims game object: Our character is a child of a new game object, FaceAnims. This allows us to be able to animate facial expressions. As our character has its own Animator component and its own animations, we cannot modify it with the Animation View. Adding a parent game object solves the problem.
• Direct Blend Tree: We use a Blend Tree set to Direct. This allows us to blend multiple animations at once. This is suitable for Blend Shapes and facial expressions.