I have tons and tons of bettas so I use the dishwasher in the jars and ten gallon tanks. I'll use the same for my bp's 10g. Once she grows into the 29, we'll do it the way we use for our bigger tanks.

drag the tank into the tub, get a dish scrubber where you can prefill soap into it and scrub like mad. then we use our hosed shower head set to scalding and rinse thorough. once dry, we check to make sure it's perfect and if not, scrub down again. We also have a shark steamer to use on funky containers to kill bacteria.