Scratching (also known as “flashing”) can be several things, such as flukes (which your 3-5 min. freshwater dip should reveal), Ick, or Velvet. They will eventually all irritate your fish, especially when the gills get fully targeted.
Read up a bit on the freshwater dip, but I just did a Wrasse, Dwarf Angel, Tang, Puffer, Longnose Hawk, and others— I used a air stone and periodically pulled it out to make sure the fish was still breathing (hard). Breathing hard for 3-5 minutes is OK. Not breathing = not good (lol)!
As to your other question, for something such as a burying Wrasse, you can place a small Tupperware bowl of sand in your QT tank, but it could get messy. I just make my Wrasse wedge in between PVC or a something else for a month—“too bad”— I’m trying to save your LIFE, Mr. Wrasse :)
Someone else will have to tell you whether the pods will survive copper; but know that “some” fish will lose the majority of their appetite while under copper.