This started out as "light" version of Jim Talbot's method to flatten a face and apply a decal but it's already running long...
Episode 1 is on Youtube. How to flatten a face?
Episode 2 is on YouTube. Fixing the overlaps.
errata: at about 11:30 I say "This character has a very long protruding feature in the nose..." when i really meant the chin.
Episode 2 Addendum is on Youtube. About those hidden splines in back
Episode 2 Addendum-da-dum is on Youtube. Not strictly required viewing, but this covers some more examples of re-apportioning patches for bitmap coverage.
Episode 3 is on YouTube. Capturing the wireframe, sizing it correctly, and painting on the decal.
Episode 4 is on YouTube. Discussion of what we need in a paint program. You can skip this if you are already quite familiar with AdobePhotoshop.
Episode 5 is on YouTube. We finally paint our color map.
errata: at about 13:50 I demonstrate a very soft brush but the screen capture loses most of that softness. You'll want to experiment with that yourself.
Episode 6 is on YouTube. Bumps and Displacements.
Episode 7 is on Youtube. Controlling hair with a map.