I never pre-wash pre=cuts. I've used lots of flannel over the years without pre-washing and have never had any problems with the end result- my sister's flannel crazy quilt I made even had a mixture of pre-washed, not pre-washed and regular cottons- the quilt is beautiful, and has been washed many times. shrinkage is one of those things that is 'relative' the batting, backing, and density/type of quilting all play their parts. I would wash the finished quilt in cool water & tumble dry on low heat- it will turn out fluffy, soft, warm & cozy.