I have shrunk warm and natural both in the washer and by hand. one of the reasons I like warm and Natural is it is a sturdier batting when it comes to preshrinking. Soak the batting in the bathtub, but put the batting inside a plastic laundry tub. Warm and natural has a tendency to float , so keep submerging it . Once all the fibers have been completely saturated with water , drain the tub, and press out the water from the batting. Use the laundry tub to lift it out. If you can use a spin only cycle on your machine , use it to remove the excess water. If you can't spin just make sure you press out as much as you can prior to removing from the tub. Then toss in the dryer. ( I suggest the plastic laundry basket as a wet batting is heavy , and pulling on it while wet can damage the batting, and the handles on the basket make it much easier to maneuver.