If you have the room, you can drag a Crown out of the wind window and the sail will luff. Usually however, we simply gather all the bridle lines together at the swivel and then walk toward the sail. As the leading edge is drawn together, the sail will collapse. If the wind is stronger, we will sometimes put our arm over the bridles. You can also use a large ring or carabiner, or throw a strap over the bridle and use that to close the Crown.
Large kite require constant attention in unsteady winds.
That's just a fact of kiteflying life. Jerking the line doesn't help. That will just increase wind problems when you stop pulling. One answer is to stand behind the crown and grasp the trailing edge with both hands. Hold the fabric about two or three feet apart and pull your hands together.