When I made my CR quilt I used 2 products that are a must from Dharma Trading Co.
Professional Textile Detergent
http://www.dharmatrading.com/html/eng/4986873-AA.shtml
Dye Fixative
http://www.dharmatrading.com/html/eng/1569-AA.shtml
The bags are flannel and very easy to work with. I washed them before cutting or removing the drawstrings. Since the fabric is not really meant to be washed, the detergent and fixative help to remove any migratory dye and to fix the set dye. Once they are washed and dried, you can really see the color differences and sort accordingly.