When Kasane and I do serpentines free-lunging, I usually only have my carrot stick (4′ stick used for cues with a six foot lash). You are right in that most of the cues she is working from are body language and voice commands (walk, trot, reverse, etc.). You know how you can feel when your horse is hooked on when free lunging? It’s like that, except we are in the big arena and not in a round pen. Usually when I stop and stand still, she will move around me.
If we are going clockwise, for example, I direct where she is heading by pointing with my right hand. I keep my hand low and use one finger for walk, two fingers for trot, and three fingers for canter (plus voice commands). My left hand (holds the carrot stick) raises and lowers in response to how much more or less energy I’m asking her for. When I want her to move out more I’ll raise my left hand. Most of the time I keep it low so there is no pressure on her from it.
My body is usually placed in the same triangular location as if I was lunging her on a line. My shoulders are square to her when we are moving in a straight line. When I want her to turn, I open my body language to the direction I want her to go. If I want her to turn towards me, I step slightly behind her shoulder and towards her rump. I point with my right hand and invite her to move that direction.
Using this method, we can do figure 8s and move up and down the ring while free lunging. It’s worked well at the walk and now we’re doing more at the trot. (Some times she will even let me direct her over the jumps, too, but that’s trickier because once she starts to approach a jump, she has to take it.)
That’s what we did tonight too.