There are either joint-based or blend shape-based approaches for rigging a face.
Joint-based systems
A joint-based facial rig utilises joints and skinning to affect areas of the model.
A joint-based system can be directly attached to the skinned (main-rig) model or offsite on a duplicate model and then connected to the main rig using a blend shape.
Joint systems can also be used on duplicate models as part of blend shape systems. For example, to help create a rotation for a blink or eyebrow behaviour.
Blend shape (on or off site) systems
Blend shape systems use duplicate models to create distinct shapes(targets) for movement.
You can either use fully duplicated models (offsite) or create (onsite) targets to create your system.
Offsite (full duplicate modelling) allows you to use sculpting tools because you are not directly altering the skinned mesh. A full duplicate can also be exported out to ZBrush for sculpting or to be archived
Onsite (skinned model modelling) means you are unable to use full sculpting tools because you are altering a skinned mesh.
cheek thinning blend shape using the shape editor
select the face mesh create first one empty blend shape and afterwards add some targets to it. when creating the target to edit the mesh the “edit” button should be turned on (red)
to make the edit definitive use the set driven key editor with the joint as the driver and the face shape as the driven with the corrective shape selected
sculpt tools (shape authoring) designed to work with blend shapes- erase and smooth and soft selection
pull out and in mouth target same process to push further the pose and keep the target value to 1 duplicate the target twice put the finial target to 0 and the second to 1 and the third to a 0.3 0.4 value merge the second and third targets and delete the first one: now the pose is pushed further and the value is still on 1.
curl in and out and pull in and out lips blend shapes once created they can be added to the rig using the set driven key editor where the driver in this case would be the mouth control and the driven the blend shapes all the key created have to be set as linear tangents in the graph editor.
Once every shape is created they should be connected to the face controls through the set driven key editor.