My method is similar to one posted above, with more steps:
I first rinse the keg out with hot water to get any yeasty sludge off the bottom, and then put about two gallons of hot water in it. I then put a little pressure on it and force the water through the beer line. Once that's done, I put 2 gallons of hot water with 2 scoops of Sun Oxygen Cleaner in it, throw on a little pressure, and push just enough through the beer line that it starts coming out of the tap. I close the tap and wait 10 minutes. After 10 minutes, I push all of that out. The keg gets another rinse with hot water, and two gallons of hot water goes in it, and I force it through the beer line to clear out the cleaner. I then take the tap off, disassemble, and rinse it out, and put it back on the tower. Afterwards, I push about a gallon of StarSan solution from my dedicated keg through the line, and then pour it back into the StarSan keg when I'm done.
The empty keg just sits around with the lid open until I need to use it again. When I go to refill it, I rinse it out, take it apart and rinse the pieces to make sure nothing is left in the poppet springs, and push some StarSan into it via the liquid out post with the lid pressure release valve open. After a good shake I push the StarSan back out into the dedicated sanitizer keg, pressurize with CO2 and release a few times to purge any air still in there, and fill the clean keg. Those poppets have to be clean and sanitized as I fill through the liquid out post with the lid on (pressure release valve open) from the racking port on my Better Bottles. I always spritz some StarSan from a spray bottle on the posts and QDs before I connect to do the fill.
I do this for every keg, every time. It's more work, and I do "waste" a little CO2 doing it, but I feel secure that everything is clean and sanitized.
