Well, I use Cupramine in my QT as a preventative treatment for all my new fish, unless they're especially sensitive to copper (e.g. mandarins or puffers, maybe others). I do a very large water change (basically drain the tank and refill) but I don't completely tear it down and scrub it out. I'm replacing the copper, and the ich or whatever had better be dead as a result of said copper, so its pretty safe.
I would not put an inverts, including corals, in my QT tank however. If I need to QT something like that, it will have to go into a different tank. I suppose you probably could clean it out really good and then use it for inverts, but I wouldn't take the chance, personally.
jds