Usandpets described, more or less, the method I would use. YOu push against his front end to get it to move away from you , which causes his side to become available to you where you can then put pressure on his driveline area (just behind his girth area).
When I do this, I have the horse on a long lead (I prefer a heavy cotton rope to the traditional lungeline) and I stand off from the horse about 5 feet. He looks at me, I look at him squarely at his nearest nostril. I mentally push on that place. I walk toward him with my feet pointed in the direction I want him to walk out toward. I swing the rope or whip, as explainded above, and literally move toward that nostril. I will tap my fingers near the face/upper neck and if I get so close that my rope propellor actually runs into the hrose, it will whap the upper neck but my mental focus is on the near nostril. Once it whaps the horse, he'll jump back indignantly and as soon as he has moved his head away from you , take one stap more toward his midline and put the pressure on his side/bum which says "go forward".
If he rears or jumps around , he IS confused, so don't worry. He will find the correct answer, but don't give up pressing. If he gets really upset when you try to put toghether two thins: move your head over AND now go forward,
break it down into two parts. Move your head over. He does, you release pressure and let him stand, and then do again. Once he will step his head/shoulder out easily, then ask for that AND now go forward. keep inmind what you are asking, and reward only for that, but never fail. Dont try to get it all at once.
You horse is not trying to make your life difficult. He probably thinks you are doing that to HIM!
Tell us how that works, ok? Good luck