In this move, you are creating the illusion that a strange itch is travelling around your body. As you reach to scratch your body make contorted shapes, with lots of bent elbows, turned in knees and cross body movements.
You can make really big shapes or understated but your face must show that something has 'taken over' your body. So you're going need to act your little socks off for this move!
The movements are quite sharp and staccato and the feet can stay on the spot or you can travel slightly with this move. Ultimately it's an improv mood so it's not codified what shapes you make or how you style them.
My main tip is you need to be fully committed, if you hold back a bit then you can end up looking odd!