I have used wool batting twice. I did not prewash it and I washed my quilt after I was finished and the batting was great. It is lighter and fluffier and was easy to hand quilt but I did not like that it slips and I had to be more careful about puckers. When I use cotton the cottons seem to cling together but with the wool the cotton top and batting could move. I pin when I sandwich and so maybe I am not careful enough. Anyway, no problems about washing. I do quilt pretty heavy so I don't know about how far apart.