I use Hobbs 80/20 and I do not pre-wash my batt. It has a shrinkage of 2% when washed after quilting. I machine wash my quilt with Shout color catchers and put in the the dryer. I take the quilt out of the dryer before it is totally dry and block it out on the carpet (out of traffic area!) It usually will finish drying overnight and comes out nice and flat, no wrinkles.