Well, like I said before, you could use it in a QT, but I can’t say for sure that it would be nearly as effective as the tried and true methods. That’s really not what this was meant for - if I was going through the trouble of QTing, I’d personally want something more certain, since I still don’t know for sure if it eradicates or just controls an outbreak.
If you did use it in a QT, and you’re doing the two 150ppm baths 6 days apart, I doubt it would hurt anything to also dose a few times a day. I don’t think anyone here has gone higher than 1mL/1gal, though, which works out to 7.5ppm. I’m sure you could go higher than that in a fish-only QT, I just don’t know how much higher before it starts stressing the fish. I think even the low doses irritates their gills after a while - I still regularly saw flashing at the 1mL/5gal doses, but it stopped completely after I stopped dosing,