I decided to cancel this tutorial for several reasons.
1) I needed to use a band saw to cut the wig-head. Using a knife and it was far too difficult. I want to keep my tutorials as crafter-friendly as possible, and using heavy machinery won't make it.
2) Try as I might I couldn't get a clean look. Too many bumps and bits made the adjusted head look like someone had taken a sack of doorknobs to it.
3) There are pre-made alternatives.
With a bit of looking you can easily find a Wig Block. A wig block is nothing more than a canvas or wooden knob roughly the size of a human head. It doesn't have a face like the Styrofoam heads that are everywhere. You only have a general noggin shape. However they come in various sizes so you can easily find what you need. They're sold by the circumference of your head (the tape measure will cover your eyes). I personally am a 23 (fyi, the average Styrofoam head is a 22).
You can find them at most theater/wardrobe supply shops, but it's doubtful you'll find them in the everyday costume shop or Halloween store. Average price is around $40. Make sure you get a canvas wig block since I'm pretty sure nails are a little hard on wigs.