Full Swing · Feel

Set the trail arm palm-up like giving blood

The coach's core feel for the trail hand through the backswing: feel like your trail palm is facing up toward the sky and your trail elbow is set as if you're about to give blood, and hold that same feeling from the setup through the takeaway to the top. The trail forearm should stay perfectly level, not tipping either way. He frames it as giving blood with that trail arm to start.