I use Revive personally but I would assume 3-4 drops at most - that stuff is pretty strong. I'm sure others who use it will chime in. Kraylen uses it while propogating I believe.
It says to use as a dip do like 40 drops to a gallon.
I was fragging some zoas the other day and used two drops to a smallish little cup of water and dipped the coral for about 5 minutes and those coral are all great looking 20 days later.