Looking for Advice on Tank Transfer

[gregzz4]

Starting bare bottom is definately your safest option.

I recommended using as much old water as possible as this will, in my opinion, cause the least amount of stress to your corals.
Whatever new water you need to use, make sure you test and dose it first to get the big 3 matching your old water - Alk, Ca and Mag. And aerate it well to off-gas the CO2, bringing the pH up. I do this overnight as it's part of my routine before a WC.
I use a Maxijet breaking the surface for this.