I don't prewash, but I do soak and spin the batting, then into the dryer until just damp, lay out flat until dry. I have also taken it into the shower with me, roll up in a towel to get the excess water out and a quick spin in the washer. Again, pop into the dryer. I have gotten busy and let it fully dry in the dryer with no problems. I tried the spritzing with water and then dry but it didn't shrink and when I washed the whole quilt it did, so that trick didn't work for me. Really depends on what finished look you want.
bev. :)