The only fabrics i prewash..are dark solids..and flannel if i am mixing it up with cotton in a baby quilt, and Batiks.
i have never prewashed batting, and have never had a problem with it either..i use W&N about 90% of the time.
I always use a color catcher,if i am uneasy about the quilt colors bleeding.better safe than sorry.
I have used loads of charms and maybe a half dozen or less jelly rolls, and have never had a problem with them bleeding. Never. all were Moda,i believe.
when i learned to quilt, i was taught to pre-wash, and did it religiously..but i found that anything that had some sort of stripe,wether it be flowers in a row, or regular stripes..it all went wonky after it was washed, even when i started hanging it up to dry. they still went off course..so i quit washing fabric..
I love the way the quilts looks when it comes out of the dryer..for me it is the exciting part of the process..making it though the washer and dryer, with no seams that came apart, and looking all warm and cushy..and almost "old" looking.
to each his own..i just don't. i don't have that many good days in my life to spend in washing my quilting fabrics! lol!
besides, i can't get up and down my stairs like i used to,and to begin with, and my husband does all our laundry..Bless his heart..he has for years..i would feel bad if i added quilting fabrics to his laundry list! 8-)
This is all IMHO only...of course!