andy,
I'm not sure where you read to always drip acclimate your fish - that certainly isn't true. There are specific cases when you need to do that, but it has to be done carefully, and for the proper amount of time. Too many people don't aerate the water, or take too long, harming the fish. You need to monitor pH, temperature and specific gravity of the tank and the acclimation vessel during the process, otherwise - you're just guessing at the rate. I only drip acclimate when I have fish that have been shipped for 36 hours plus, and need to be moved to low pH, zero ammonia water first, or when the specific gravity is substantially higher in the tank (but then I prefer to lower the S.G. of the quarantine tank to match that of the shipping bag).
Freshwater dips have no benefit for disease control - the only use for them is as a diagnostic tool to check for flukes. After a five minute dip, you check the dip water with a hand lens of low power microscope to look for flukes. I've never used freshwater and formalin at the same time, but five minute formalin dips are useless - the shortest time there is a published reference for is 166ppm formalin for 45 minutes.
Jay