Dead red bugs on the bottom of the dipping container every time using bayer for me. AEFW shrivel up and die and melt.
Bare coral in Bayer - no plugs or rocks but this is easy for me since I only really do acropora. I pour in the bayer until I cannot see through it - I don't measure or anything, but I use a lot, like maybe 10-15%.. I use a look-down viewing thingy so that I can see into the bottom or shine a flashlight up through a shallow pool as I pour it off to see what fell off of the stuff. I use so much bayer that it will bring the temp down and I heat it up first. I turkey baste the frags every minute or two for 15-20 minutes. I grab the frags out of the mix with tongs and put them into a fresh container of saltwater to observe. They rarely slime. Then I pour out the bayer slowly without disturbing it and see what is left in the bottom.
I am really easy on this... if you get red bugs or AEFW, then it is on you and you alone. Some think that this is harsh and do not want to hear it, but from the other side of their mouths most complain about the cost and price of corals already and have no idea what a vendor goes through to get these ready to sell in both actual hard costs and time. The good ones do the best that they can, but you need to expect non-perfection and have a plan on your side. I know that our LFS has at least regular red planaria and who know what else - again, they do a good job which is all that I can ask and the rest is on me.
I still use a Coral QT to observe and retreat if I need to, but I have had no issues since I quit CoralRx/Revive and went to Bayer- that stuff worked, but was harsh. Red Bugs are easy to treat, so I am not scared of these. I am still wary of AEFW, but since I have had good success with some of the locals using a long, and expensive, trip to AEFW eradication using KZ, this is not as scary as it once was, but I want to avoid it still. Coral QT is the only way to guarantee that nothing gets by...and smart management not adding and taking things out of it all of the time.
You can see Red Bugs and/or AEFW on frags if you look close enough. Bite marks are easy to see and the Red Bugs are usually near the polyps. Both can hide on the frag plug, so I remount. Get a handheld loop and a bright light if you need one. Even if you don't mix your dip strong enough to kill them, they should fall off in the water, so inspect it before you put the frags away and re-dip if you need to.
If none of you have ever gotten coral eating spiders, then that is a really scary one. Never had them, but had a friend who you could see them walking around. They just went away and he has no idea what he did. They seem easy to kill with most dips, but they are hard in-tank. They can hide, along with so many other things, on larger rocks full of Z&P and corals that are hard to dip.