I agree with pre-shrink atleast one time. I always use a "colorcatcher". Bad experience, even after I pre-washed all the fabrics for a quilt for daughter. So please don't take any chances.
Pre-shrink on the advice of an Extension agent and Home teacher and just plain sewing/quilting experience. ***Always pre-shrink/prewash and always when making Rag quilts, use the laundramat to "rag out". It's too hard on your machines. And the laundramat machines, the heavy duty ones are more industrial for this type of step in quilting. I've also used the laundramat for the doing the Faux chenille scarfs that are made of flannel.