It took almost a week to fill up the tank with new RO water. During that time, I added salt every day and kept track so that I could keep the salinity near 1.025 the whole time. Of course, I was just taking cups full of salt and throwing them in the tank, while I had all my pumps running to mix it up. Once it was nearly full, I added the sand. That caused the tank to get cloudy for nearly another week. While the sand was settling, I started moving my rock into the tank. The plus side, was that I was able to get the tank ready more quickly. The down side was that I had a difficult time seeing where I was putting the rock.
In hindsight, I would probably add all the rock at one time while the water was clear.
I would say the water was in the tank for almost two weeks from first day of filling the tank to adding the first fish.
I kept the salinity and temperature of the new tank the same as the old 75. I netted my fish from the 75, put them in a bucket (one at a time) and moved them into the new tank. Basically zero acclimation. I moved a powder blue tang, purple tang, flame angel, damsel, 2 clowns, and a goby. I also moved all my corals at the same time as the fish. I know a lot of people on here are ultra careful with acclimating their fish and corals, but I have had zero deaths in over 3 years with minimal acclimation. I think people over complicate things sometimes. I attribute much of my success to my very light bio-load for a 210. I only have 7 fish, and none of them are over 4-5 inches.
I would run out and buy a step ladder. My tank is on a 36" high stand and I am 6'2" and I use it every day. I can see why people get tired of dealing such a tall tank.
Good luck. Let me know if you have any more questions.
-Jeff