I’ve made several rag quilts from flannel. A few years ago the local laundromats started posting signs of “no rag quilts” because the lint was killing their washing machines. So for the first two or three times of washing this is what I do ... take an old sheet and sew up 3 sides .. put your quilt in the “sheet bag” and sew the sheet bag shut. Wash in your washer. Take it out of the washer, go outside and use scissors to cut one seam open. Shake the dickens out of your quilt and pull out the big clumps of strings from your bag. Put the quilt back in the bag and sew it shut. Wash again. After the wash, again take it out, shake shake shake, etc. Put it in the dryer and set a timer for 10 minutes .. every 10 minutes clean out your dryer lint trap. After drying, take it outside and again shake shake shake and pick off any big clumps of strings ... now you should be able to wash it again without the sheet bag ... then dry checking your lint trap every 15/20 minutes. If your rag quilt is strictly cotton you should only have to wash once in the sheet bag ... if it’s from homespun fabric you’ll probably need the bag 3 times. That’s my personal experience anyway.