Let me ask a question first before I give my 0.02 worth. Why do you want to clean it?
My experience right now is I am not going to clean any of my dead corals. First, it probably has some good bacteria on it and cleaning it would remove it from the system and introduce new unknown contaminates to the tank. Second, I tried to clean mine and I screwed up and did not properly remove the cleaning solution from it and my tank crashed and burned. Third, I am trying to build up my "cleaning crew" to do the cleaning for me. I think it is doing pretty good, I just need a few more snails to assist with the tank walls.
So, the best way to clean you decorations is to get a cleaning crew, i.e. some snails and hermit crabs. Right now I have 2 hermit crabs, 2 snails, and 1 cleaner shrimp. Only the walls need more work, hence I want more snails.
HTH