why would you want to wash your batting before finishing your quilt?
the package will tell you how- if it is something that you should do-
the only time i can think of i would even consider it was if i went to a woolery and purchased a raw-wool batt and it needed to be washed- any commercial batt i would never consider washing before my quilt was quilted and bound
but the packaging tells you a wealth of information- and i'm sure different batts have their own instructions/recommendations where pre-washing is concerned.