I, too, use flannel for my rag quilts.
I do take it to the laundromat to finish the ragging process there - after snipping the fabric at home I take it to the laundromat, get it wet, and put it in the industrial sized dryer without heat til most of the threads drop away. I end up with a whale of a lot of thread lint this way. When no more thread lint, I dry the quilt.