Well, most of my personal experience has been with fresh. It was about 30-45 minutes of bag float with a cup of water from aquarium into the bag every 10-15 minutes. Then net the fish and put em in... never lost one.
Now salt, my dad has done for over 20 years. He did bag float too, but his was about an hour float with water added every 10 minutes. Again net and in. He doesn't recall loosing any in the first month... So it works, but he always bought from the same store and to his memory his tanks and theirs had the same temp and salinity and aimed for the same pH. That probably helped immensly. Just had to deal with temp change from the trip home. He always talked with the guy at the store and saw the store water parameters and matched them.
As for me with the fresh....well many came from *****, but some from other stores and I never "synched" water parameters. However, drip makes sense as a more gradual peaceful method. That being said, bag float works....