The original article from Studio Daily, Giving the X-Men a Digital Face Lift, can be read here
I didn't pay much attention to these details in the movie. But reading how they did it I realized it is quite a feat, and it's on motion picture!
They currently go so far as tracking small camera movements or actor movements. Given a few years, we might not need to find the next James Bond after Daniel Craig. Use computer to make Sean Connery looks younger and you've got your man.