You are on the right track. Let the tank sit with no fish for 6-8 weeks. You can add coral and/or inverts as ich does not and can not live off them. There is a slight, extremely small chance that the coral/invert can be carrying ich when it's in the trophant(tomont cyst) stage. That cyst can then hatch and start the infestation. The cyst can live 6-10 days without a host fish, then it dies.
Ich is either present on a fish or not present. There is no "sometimes it has it". It can't die off and mysteriously reappear. There are 2 100% scientifically proven ways to kill the cryptocaryon (ICH) parasite. Copper treatment or hyposalinity. Not garlic, not vitamins, not hocus pocus magic reef safe potions. Copper or hypo....period. If you properly treat a fish that had ich, it WILL NOT RETURN unless the parasite is introduced again. You can treat and cure a 15" sohal tang, put it in a 10g tank by itself, and even tho it will be stressed to the max, it WILL NOT GET ICH AGAIN. It is a parasite. A living organism that doesn't appear out of nowhere.
If you wait the 6-8 weeks with no fish, make sure you quarantine any new fish and watch for problems. Without quarantining new fish, you can introdice the parasite back into the tank and you will be back to square one.
Sorry for the rant. Ich misinformation kills me.