I prewash my batting like Cathe - soak (don't agitate), spin, and dry in the dryer. I just like the 'look' better. As for washing after it is in the quilt, I wash on gentle and air dry on a rack. I don't put it in the dryer. I think my kids wash their quilts like they do their jeans and they are holding up fine. Well, maybe wearing out a little quicker.
Judy