Some people, myself included, dose Cupramine over 4 days rather than 3. The bottle says to put 1/2 in on day 1 and 1/2 in on day 3. I put 1/3 in on days 1, 3 and 4. It gives the fish more time to acclimate.
I use a lower dose like .3 to .35 when the fish show no signs of parasites for 3 - 4 weeks. I would use the higher dose if I saw parasites on fish.
Although Cupramine is very stable in solution, you should still test. I have the Seachem test, and it is somewhat hard to read. I would try the Salifert test kit.
Flame angels are very sensitive to copper and you may not want to dose them above ,15 or so.
Watch your fish carefully. If they appear lethargic and stop eating while undergoing treatment, reduce the dose concentration or better yet remove them from the copper solution (i have a second qt for this).