Recently added 2 large pieces. I poured hot/boiling water over them in a large plastic container and let them sit, changed the water every other day for right at 2 weeks. Every couple of water changes I would pull them out and scrub them down and spray them off. It worked out pretty well for me (no yellow tank). I'm sure that I rushed it a bit but as long as the water you are draining out is clear I'd say you're good to go.
I would def, recomend boilling if you have a large enough pot/small enough piece.