This is how I do it. I was sick of trying to get them clean (bad back makes it hard really). I also thought this would not work out well, but I've been doing it for years after every brew session. I used to fill with water and PBW then heat and circ the water for a while, but that seemed slow and inefficient compared this method.
I wouldn't do it if it wasn't very easy for me to replace an element. Haven't had to yet! I use the ubiquitous Camco #2963 5500W incoloy ripple. I think others here have said SS elements will split if you dry fire them.
I hit it with 100% pwr for about 15s, until the green smoke starts billowing out of the kettle. Then off, clear the smoke, then back on again until the element is cherry red (only red for a few seconds). Then I let it cool completely, then spray with hose. Perfectly clean every time.
[ame]https://www.youtube.com/watch?v=nKG3UjT0Wz4[/ame]