After you treat Ich administer hypo before fish addition. While the fish are in hypo do water changes every day. Wash your hands before touching your main tank.
Don’t add water from your LFS or you may introduce Ich again.
This thread deals with FRESHwater ich (Ichthyophthirius multifilius). SALTwater ich (Cryptocaryon irritans) is an entirely separate species which just happens to manifest the same symptoms.
One cannot apply the treatment of FW ich to SW ich or vice-versa. This is why I don't think the whole "raise the tank temperature" thing can be applied to SW ich.
According to scientific literature, any "cures" involving garlic are purely anecdotal. It's very difficult to be sure if ich is still present because it may simply be that your fish aren't showing any visual symptoms. Low level infections that "pop-up" is not proof that ich is always present, but rather that the infection was never fully eradicated in the first place.
The only sure ways to kill ich in a tank is either hyposalinity or copper.
I fought an epic multi-month battle with ich on my hippo tang. Had I not quarantined him (and everything else) to begin with, I surely would have been in big trouble.
In the end, only copper medication finally eradicated the parasite.