Have a partner hold one of your hands and twist it so the shoulder becomes tense. Keep breathing and feel where his direction is heading and align your body with it so you can escape without trying to overpower him. Fore example if he turns your hand so your palm faces you and bends your fingers toward you, you can take one step and and place your entire body in the same direction. It is a matter of joining his movement and adding to it so there is no tensing up or resisting but you have to keep moving otherwise it becomes a drill or counter action which is reaction rather than action. Keep moving and you will stay alive.
I am writing a starter base program for solo and starting group for Systema students which I will post in a few weeks. If you have any questions, suggestions or requests please mail me at firstname.lastname@example.org