are you lunging with a traditional lunge line, or a long lead line? I would start with a regular/long leadline. this keeps the horse closer to you. (not so close they'll cow kick you, though).
the whole idea of getting a horse to move their sholders away from you is a valuable thing in other ways, too. it's at least as valubale as having the horse move his hind away.
here's what you can try:
so, your horse is standing facing you. you are off about 6 to 8 feet, and you can be smack in front of him but it's better if you stand just to one side, like off at a slight angle from one or the other shoulder. lets say you want to make the hrose travel to YOUR left, so he's circling counter clockwise.
you lift your leading hand, your left, and put a little "feel" (a kind of weight or pull) on the line toward that didrection. you turn your body slightly in the direction, but put your feet so that that are pointed at his nose, angled in that leftward direction.
put a few tugs on that rope to say to your horse "this way", and back it up with a little wiggle of the whip that is in your right hand, off to your right.
as he ignores this, or is confused, you start to focus more of your intent and energy on his NOSE. his inside (closest to you, his left, nostril). I use my driving hand to actually start "air poking" rythmically toward that nose, while still indicating what with the leading hand to go left. I walk toward the hrose , giving him many chances to respond and step AWAY from me, toward the left.
he may back away, if so, I keep approaching, keep lightly tugging with the leading hand to go left, and keep my body drive focussed on his nostril. I am getting him to eventually move his face away from me, then he will step his shoulders out and away from me. I might have to go so close that my air tapping fingers now tap sharply on his cheek or the left side of his nose. he WILL move his head away, and his shoulders will follow, and he'll step out away from me.
this puts him from having his head nearly straight at me, to having the side of his body available to me, and now I can use that whip or my body language to drive him forward. it's important to keep up a feel of a forward tug on the line initially, becuase if I am just driving him, he will back away, or turn to face me. it's the combination of that leftward "feel" on the line AND the driving that gets him to follow the pull on the rope and start to walk forward.