Actually, this tutorial is not mine. Great thanks to
Model used here is Anime Painted Miku by tk. She requires using AlphaEye to make her mouth visible. Download her here: [link]
Video example [link]
The same in Russian [link]
Kagamine Rin by [link]
AlphaEye MME by beamman [link]
P.S. AlphaEye is not compatible with shaders or any other effects which are applied to the model.