Does the vertex count match up twixt scanned head and original ? In virtually all the software used to create 3d faces that seems the problem most of the time. There are are ways around it...for example for face gen.. http://facegen.com/customizer_tutorial.htm ...though as you noticed it's way way complicated stuff. So yea your workflow is looking pretty good for a static head, sculptris can also paint as well.

Pinky - you left the lens cap of your mind on again.