I use a Python hose/siphon system to vacuum out and re-fill the water. No buckets, very handy, money well spent!

I have a digital probe thermometer (from the kitchen) that I use to test the water from the faucet for temps (my hand isn't as finely calibrated as Tom's ).

I just add the water treatment (we sometimes have high levels of chlorine and chloramines so I like to treat for them) as I start to fill the tank like Tom does. The water addition seems to do a good enough job of mixing in the chlorine remover...