I never prewash anything and have made quite a few flannel/cotton quilts as well as all flannel. I've never, ever had any problem with any of them shrinking enough to be a problem either way. I always wash in cold water and dry on low heat in the dryer till almost dry then lay out to finish drying. They do come out with the nice, even wrinkly look. I use Warm and Natural batting in all of them.