7/8" 12 point box end wrench (or the fancy socket they sell online).
Long dip tube brush is nice too, but cleaning them out right after they're empty is so much easier than scrubbing a bunch of dried up gooo.
Seems like 5 or so batches is the general consensus, but between batches a hot water rinse, invert the keg and get everything wet. Vent the hot water through the gas & beer ports/tubes with the keg upside down. Drain everything, including the poppets upside down and let dry (upside down with the lid off). Then I just run iodine solution through the keg and all the tubes, then rinse right before kegging.
The drain/hose bib on my hot water heater (conveniently located near the back garage door) is a great source for really hot water as long as you keep it flushed on a regular basis. The scale and particulate that accumulates in the HWH settle toward the bottom drain. I have a short hose for hot wash and rinse that I hook up, and even made a hose end fitting that hooks up to the #4 flare fitting on the black "beer out" ball lock fitting for back flushing the keg all the way down the dip tube. The water pressure does a pretty good job of knocking out the crud, but the biggest thing with all my gear is to keep it clean right after use. It's less hassle that way, the next time I need it.