Why not do hyposalinity? Angels are not good candidates for copper treatment. Are you setting up the QT now, or is already cycled? What about other fish?
I have a bar goby, and a chromis. I used some kick ick and it seemed to help a bit, none of the fish now have any really bad break outs but I read in one of your posts that once ick is in your tank it’s in there and the only way to get rid of it is by hypo or copper. I had posted this question before and the responses where pointing towards copper. And as for setting up the QT in that last post you recommended that I use 50% water form tank and 50% new water.
Yes, copper and hyposalinity are the only viable treatments. Products like kick ich do not have a good track record.
If you water quality is good in your display, and you can spare to use it for a QT, then go with 100% water from display for the QT.