To take full advantage of this character rig, the latest BlenRig addon needs to be installed.
In the MUSCLE SYSTEM tab of the BlenRig UI, you will find a property called "Deformation Extras". This property toggles some modifiers in the viewport that will enhance facial deformation. Note that this does not affect the rendering of the character, as those modifiers are always on for rendering. By default, Deformation Extras is off, to have a faster playback.