I've used them on all my purchases before putting them into the Q tank. I've had no problems and a high survival rate. It's probably less stressful to use hypo, so will do so in the future.
In any event my fresh water procedure consists of the following:
Put 5 liters of filtered fresh water in a pail(even though it's gone through a good filter, I still add a couple of drops of declorinator to be on safe side), of course the tempature s/b exactly as the Q tank. I add a teaspoon of sodium bircarbonate( baking soda) to get he PH to the same level as the Q tank. I then carfully remove the fish either by hand or net. I release him into the pail and watch closely. Some fish seem to adapt to the dip quite well. If he starts to stress out, I immediately take him out and into the Q tank. Do not add any medicines at all to the fresh water. It does sound a bit stressful but like I said it has worked.
It's quite interesting that most who use this, do so to avoid using a Q tank. I do not advocate this because when the fish comes out of the fresh water dip it needs some time to recover and the last thing it needs is to be chased by a territorail tang or other fish. Always use a Q tank. Good luck.