I hold my son's head with my right hand, the left hand scooped under his butt. He screams. I bounce. He errantly flails his hands. I bounce and "shushhhhh". He kicked his legs with all his might. I bounce.
Slowly but surely, he gets a little more limp in my arms. His eyes start to get heavy, then close intermittently. Eventually, he will slump entirely into sleep.