I use the salt and cold water, too! Even red holds it's color so well. My husband won't wear new jeans until I was them at least twice in salt water. He doesn't know it's salt water, he thinks I'm magic in keeping new denim from fading on him...
As for flannel for batting, love it love it. I often use flannel to back my fleece blankets, too. I made a friend of mine, living in Tampa, a quilt for her 89th birthday this past fall. I quilted with flannel, she tells me it's perfect weight on her. She's a sewing expert for the last 85 years. I only have 48 years in it.
When I do baby quilts...I often use a knit cotton for the backing, it cleans up easily from baby spills and lasts forever.