Chizer & Bunoi 67 gallon

Tomorrow I am going to start washing the oolite sand and will let it run with the fresh water, to settle. It's brand new sand. Then I will drain the tank and do the transfer. My 90 is currently sumpless but is bare-bottom.

Does it make sense to transfer it all at once, or should I fill this tank with salt water and migrate it slowly? I was thinking that I could siphon all the clean water for the transfer. There shouldn't be any issues with parameters this way??