Beat the crap out of them and don't be gentle. lol. There is no special way of cleaning them. You don't need to worry about BB or rinsing them in tank water. Just clean em good.
Gave mine a rinse the other day. I put them in a five gallon bucket with tank water, put that in the tub then stepped on them a bunch of times. Drained water and filled bucket one more time w/ tank water and did it again. Practically new.