I do an approach & retreat that's a bit different. Start out touching his neck until he relaxes, then stop. Next try putting your hand a bit closer to his head & don't take it off until he relaxes. You don't have to get to his forehead or grab his ears on the first day, but you can go a bit further each day. He will soon realize that if he relaxes you will go away. Do not make any quick moves either, if you feel him try to move away just stay calm, if you jerk your hand back you may frighten him & will loose a bit of trust you have just built up.
I have a boy that was abused [i think beaten in the face, he used to be petrified] now he's a lover =]