If you use water from your main tank it won't have to cycle. I wouldn't do freshwater dips. They have to be done 2 or 3 times a day for about a week on their own. That's too much work. Just quarantine your fish with copper and leave the display tank fishless for three to four weeks with the temperature as high as you can possibly get it. That will speed up the life cycle of the parasite and it'll die faster. Whatever you do don't stop quarantine prematurrely because you don't see more spots. The ich just goes into remission for a while and pops up later. I've done that a lot of times and gone through a lot of fish that way.