The technique depends on the shot. It involves tracking and match moving. This would require a fairly high degree of knowledge of compositing, tracking, layers, perspective and a lot of patience. I don't have time to search for tutorials for you right now but there's a good one from Andrew Kramer that shows how to put a big scar on a face. Search for digital makeup and see what you get.
(Edit) Found the video copilot tutorial: VIDEO COPILOT | After Effects Tutorials, Demon face.