You can use either the D-pad for fine tuning, or the left-thumbstick for moving them quickly.

I set up the game face feature, and for the most part it looks ok, not great, but not bad either. The main issue I had was the lighting the picture was taken in. The computer/xbox interpreted my eyes and eye-sockets as being too dark, and the final result looks like I have *heavy* eyeliner on. I'll retake the photo whenever I get the time, and try again.

PS: It really does take 10-20 minutes to render the photo, so make sure you're not in a rush.