Depending on the temp. difference, I usually float the bag for 10-20 minutes & pour in about 1/2 cup at a time. 2-3 times & then I drain the bag & scoop the fish into my isolation chamber. (Don't usually use a quarantine tank - I know, me bad
)
I've also had fish that jumped right out of the bag & into the tank without any problems.
Main thing for me is to stay away from notoriously difficult fish (ie. ick magnets) like Powder Browns & Powder Blues.
Sorry to hear about your loss.
Anthony
PS. if the temp., salinity &/or pH was that far off then the basement guy's holding system was the problem since I would have done the same as you.