I wash flannel before I use it but I don't go to extremes. I wash it like I do most anything else- warm water, normal cycle, do add color catchers just so I know what's going on. Then dry it in the dryer, normal cycle. It does fray like most fabrics do. Don't do anything special about that either. Usually, as I square up the piece the frayed edges are also cut off. Most of the time I've had really good luck with the flannel and I've used many different brands, including JA and name brands. Only once I can remember after doing the prewashing and then washing again after the quilt was completed it pilled and did look a little used. Sometimes it sounds to me that people want to "declare war" on flannel and wash in hottest water, sometimes more than once. Why would you when you don't normally treat fabric that way?