Here some deformation work i did on an original design, model.
jaw rough skinning
jaw rough shapes (one for half open and one for extreme open)
It took me about 1 hrs for the rough blink, and 3.5 hrs for the jaw open rough.
Here are some of the things i found useful during creating these deformations:
1 -- having deformation reference of the action about to try to paint weights for. example film yourself in side view to get jaw open, then play through frame by frame to see what vertex need to get weighted to joint etc.
2 --Usage of Blend weight editor in actually sculpting, can get smooth fall off using the paint blend weight smooth tool. This technique together with Maya's soft modification tool are amazing at helping sculpt shapes.
3 --Using parallel blender instead of default when adding a sculpted corrective onto a skinned mesh.
4 --a possible helpful skin workflow is to use painted weights to get separation, then use sculpting with soft mods, cluster, and especially the polygon smooth tool to create shapes. A possible general workflow is to use referencing and locators to make quick technical tests of deformation.
Hope you find this helpful
Matt Estela (tokeru dot com) discussion on adding a corrective to a skinned mesh was really helpful
Michael Comet (comet-cartoons dot com) he has some amazing tools for painting weights