I use Rally in a 75-90 minute bath (for temporary relief) before placing the fish in a QT pre-dosed with CP. The entire process is outlined here (look under The short version): https://www.reef2reef.com/threads/velvet-amyloodinium-ocellatum.217570/#post-2499437 IME; FW dip + acriflavine (Rally) bath + CP treatment is the best way to defeat velvet. CP (or copper) treatment is essential, but your odds of success go away up if you do the FW dip + acriflavine (Rally) bath beforehand. Those two components are the only way of delivering some immediate relief to the fish, as copper/CP have only been proven to target the dinospore (free swimming) stage. So in essence, copper/CP only shield the fish from reinfection after the trophonts have dropped off. Using acriflavine during TTM is, of course, optional but probably not a bad idea if you have access to it. Some (on another forum) are already doing this with formalin. However, I caution to limit exposure time to 60-90 minutes to limit masking. Just in case that is a cause for concern.