I looked at a couple of my DH's flannel shirts and the label said average of 4 percent shrinkage. That might not seem like much on a 6 inch square but oh my it could be nasty on a whole quilt. Sort by colours and put in lingerie bags and wash. Empty from bags and toss a moderate amount into a hot dryer with a dry towel. You would be surprised at how short a time it takes to dry and how little the pieces will fray.