[DiverDude]

Salt mixes up right away. Some people like to wait a period of time to let things settle but personally, I take a bucket, fill it water, add salt and then dump a powerhead and heater into the bucket and let it sit while I'm at work. I do this so the water comes up to temperature; no other reason.

You can leave all your pumps and powerheads going depending on where they are. Let's say you're doing 5 gallon change; when you sipho-off 5 gallons, does the water level go the level of the pump intake (or close to it) ? If so, turn everything off.

When you add your new water, if you pour it from a bucket, it will stir-up every piece of sediment in your tank. What I do is dump a powerhead into the bucket of new water and put a length of tubing on it and pump the water back into the tank, being careful to aim the hose at the tank wall. When it gets close to the bottom, I remove the pump and gently pour the remainder in.

You'll develop a system. Spend some time getting it to work with a minimum of effort because regular water changes are important and the easier (and faster) they are, the more likely you are to do them.