I wash all quilts in cold water. I pre-wash all fabrics in hot water. Hopefully if you made the quilt from flannel you pre-washed it, since flannel often bleeds and shrinks unevenly. It's the agitation that contributes to the ragging, not the water temperature. Vinegar and salt don't have any effect on modern dyes, but some color catchers would be a good idea if you didn't pre-wash. I have read that some Laundromats have specific rules against washing rag quilt because of the same reasons some people don't want to use their home washers.