We have a couple buckets that we drilled 100 or so holes in to let water drain. We use county water that is chlorinated and wash them down real well mixing them up and dumping back and forth between buckets. Then let them dry in the sun. Works good no problems.

If you have a big bunch, get a small cement mixer electric one like slowes has. Drill it full of holes and then you can wash as they tumble too.