Hit yourself using the shotgun after the dummy bumped you (2x)
This requires you to aim at a spot on the ceiling so that the reflection beam hits you (when you start to move to the left/right). Basically predicting your movement.
You want to start to move to the left or right once you shoot the shotgun until a bit after the reflection beam hit you (dummy starts to go up again)
Every second time the laser hits you, you want to aim down in the direction of your dummy and rehook it