I never pre-wash. One of these days I'm going to wash something I've made and have major colors everywhere, but so far Color Catchers and I are best friends. I didn't use a batik back. I used a regular cotton, although my friend did use a batik and had no problem with hers. She has made several of the Hoopsisters patterns and 3 I know were batik backs. No problems. She did the Queen Feathered star on her Ellisimo and I was with her for a lot of it. Her machine chugged through it. She uses all different brands of thread, about like I do.
I am really looking forward to finding out what works for you. As a side note. If I ever do another Hoopsisters, I don't think I am going to put a backing on each piece. It will be so much easier to join all the pieces and add a backing after the fact. I am thinking that I would used invisible thread and just do a stitch in the ditch.