You will need a water storage vessle to collect the water for your water change. I wouldnt change out any more than 20 gal
of water at any one time for a regularly scheduled water change.
Its going to take quite a while to theoreticly remove all traces of tap water so I wouldnt have that as a real immedate goal.
I use 30 gal
rubbermaid trashcans to store my water change water and my top off water. One trashcan is dedicated to salt mixing and one is dedicated to holding fresh RO
water for evaporation top off. In the mixing trashcan I have a 100W heater and a medium sized powerhead. Mix up the saltwater at least 24 hours in advance so the water has a chance to come to tank temp and all the chemical reactions with the salt disolving can run their course.
Now that your saltwater is ready its just a process of removign water from the tank and adding new back to the tank. That process is somewhat unique to every tank. If you have a sump you can just pull water from the sump and add water to the sump for your water change if you dont want to syphon off your rock. On my tanks that have sumps I always add water to the sump for water changes as I find this less stressful on the fish and corals since water isnt being dumped into the tank. You can make the whole process faster and easier if you have a medium sized water pump like a maxijet 1200 or Hagen 802 powerhead to pump water thru a hose from your storage vessle into your sump. I use a maxijet 1200 to pump water from a bucket into my sump for water changes on one tank and I just pour the water in the sump on my other tank.
Total time for a water change is often less than 15 minutes for me from start to finish.