Pre-washing gets my vote. And I also follow your rule of like colors together. I even prewashed Hoffman Bali Pops in the sink. Learned a lesson there - use a bowl. My sink is tan and I had to bleach out the fabric dye. Then I spun out the excess water with a salad spinner and hung on a rack to dry. PRESSED not ironed all 120 strips. But it will be worth it when my King size quilt is done.