I've created a rig that allows for easy facial animation in Mine-imator. It consists in a surface with interchangeable textures, each one corresponding to a phoneme.
Here's the kind of animations you can achieve with it:
To use it, just make sure to edit your skin so that its mouth doesn't appear, then, import the rig and place it correctly onto your character's face.
To animate the mouth, simply change the texture using keyframes.
Here's a chart that will help you choose the correct texture for each phoneme:
Enjoy!