I made a rag quilt for my niece with lady bug fabrics. I had like 12 different lady prints or something. I used flannel and cottons. Then I bought a bit of minky and put that in it too. I did not prewash anything. And it turned out just fine :) The minky doesn't rag very well but it still looks and feels very nice in the quilt. So I just made sure that I didn't put 2 minky pieces next to each other or as as a back piece to a front. So when you sew your blocks together you dont ever sew the minky with minky. I like to sew one row with the rag side up and then do the next side with the rag down. That way both sides are ragged. And you get 2 quilts instead of one. Also if you pick a different colors for the other side the contrast looks really fun when you rag it.