Flannel should be washed - sometimes several ties - to get rid of all the shrinkage. It will still fray nicely after washing. Washing also tells you if the flannel will bleed (it does this more often than quilter's cotton) and whether it will pill (doesn't seem to be related to price - sometimes it does, sometimes not). I use a mixture of flannel and corduroy in my rag quilts, because I like the texture of the corduroy, and see no reason not to combine flannel with regular cotton if you want. You might check Connecting Threads for flannel too. Theirs seems to be a good quality, but there isn't always a large selection. I use 3 layers of flannel in my rag quilts, no batting, giving more fabric for fraying and eliminating the need for quilting through the blocks to hold them together.