Fresh Water Dip before Hypo or Copper dose

Should I Freshwater Dip my fish before I QT them to get the Ick that is on them off? They are covered in Ick and it is very very bad. Will I stress them out too bad? I know Copper only works at a cretain free swimming stage and the fresh water will help explode the Ick off the fish. How long should I freshwater dip for? I was thinking 6 minutes? Also this is important, I know Ick stays on fish for around 7 days. Is all the Ick in the tank on the exact same cycle? So whatever my fish has now, will this be it till they fall off and reproduce or is there Ick in the tank right now that can attach at any time? Thanks Again