I suggest you have an assistand with a normal short lead rope at the head if the horse has not longreined before so they can help guide,but not pull or lead in anyway, that must come from you behind. I did this for the first three or four times until he got the hang of it then the person just walked at his head without any rope and went further and further away. We started on straight lines, curves, on the road etc, and I always lunge with only one lunge rope for normal lunging in a circle.
I use the bridle for longreining, attaching to the bit, but only use a parelli headcollar for lunging. Either way with or without saddle and reins are always free and dont go through anything (no roller).
ETA Just seen the pics above, mine is not a kicker so I am only three feet from his bum, riding from the ground is fun too we do a lot of that on in hand walks........use normal reins walk at the shoulder with one hand over pony to right hand rein exactly the same as if you were on top for rein position, except you are walking next to him. Great for teaching steering on a youngster, of course if they are 16 hands you either need long arms or bring the right rein over to the left so you can reach it easier and make sure you are fit enough to keep up with their speed.