You'd have to rinse it real good first. Then you could put it in some large zip lock bags and open them slowly at the bottom of the tank to add to the existing substrate. Might make the water a little cloudy, but it will dissipate in a couple days and everything will be ok.
Crushed coral is fine. I wouldn't go to deep with it. People go nuts when certain things are brought up and crushed coral falls into that category. I have used it without issue. It all depends on how you maintain your tank. It's amazing how much mentioning certain things gets obvious replies. Go ahead and talk about getting a yellow tang in a 4 foot tank and people love to crap all over you. But someone post a video of their insane reef, chock full of SPS
corals thriving, and it just so happens to be 4 feet long........not a peep is mentioned about the yellow tang swimming around. Forums never siese to amaze me.