I use rice hulls regularly in my brewing. I put about an inch thick layer
over the braid in the tun. I add hot water to the tun to Preheat the critter.
Then I swish the hulls and hot water around to wash the hulls...Yes,
the rice hulls are dirty as you will see. Then I just open the drain on
the tun after the preheating and drain the dirty water out. Couple of times
of seeing the run off from them, no way do I want that in my beer.