I usually prewash my fabric and batting which is W & N. I'm not a huge fan of the crinkly look. However, I'll have to try Tartan's idea of blocking a nearly dry quilt to get a smoother look. I don't bother prewashing the batting for wall hangings. Right now I'm working on a quilt which has a wool batting - my first time using it. I didn't prewash that as the instructions said not to. I'm curious to see how it turns out after I wash it.