i love wool batting! i use either Dream Wool or Hobbs Wool---neither require prewashing---neither shrink---- both wash up beautifully when the quilt is finished-
i made my first quilt in 1976---and make ALOT of quilts---i have never- ever even considered pre-washing a batt. i wash my finished quilts after quilting & binding is completed- as the final step before it goes where ever it is going