Done by point motion on the fly,
It is a preparation for a 3D rig of a head with for turning. I'm planning to rig only the central points of the main shapes (eyes, nose, ears, mouth) The rest done with point motion (maybe actions)
Lessons learned:
1) For shadows insertion it s good to plan them before you draw your shapes. FOr example the lower shadow of the bear face is very bad. I should have added some points between the main ones. But now the poitna nimation is done and don't want to redo it. For the same reason I have not added shadows to the ears. Plan before draw. Perhaps a raster drawing would have helped.
2) Point motion gives a lot of control. It joined with basic bone motion is the best way to animate such kind of head turns and so on. I think that switch layer for head turns is ok but direct point motion gives you more feshness to the animation.
http://amanoalzada.iespana.es/Mohostuff/bear-head.anme
http://amanoalzada.iespana.es/Mohostuff/bear-head.swf

Enjoy
Genete