Cold water with a quality non scent detergent, say the Hunter Specialty stuff. I've owned KOM, washed it a number of times. Actually, with washing the fabric gets tighter which inturn keeps the wind out better and keeps you warmer IMO.
Just use the delicate cycle and hand stretch it when its done. Be sure to air dry. If you've got a place to hang it outside to dry, leave it there for a few days. Nothing better for removing odors. I used to hang it up in one of my trees, far enough up I didn't worry about someone grabbing it when leaving it out for a few days.