I'm reading online that I should bleach our prefolds before using them on a new baby.

they were used by our daughter (who is now 3) and some of the newborn sized ones were also used by a friend's baby.

I don't use bleach very often, have a front loader, and don't think I can do a bleach soak in my bathtub (it's an enameled cast iron?). So I'd have to soak in buckets. That will be a huge pain in the ass. We have a lot of prefolds- newborn and small sized.

I do have a "sanitary" cycle on my washer, maybe I could do that instead?