I use a regular cassette removal tool. The wrench just barely was not big enough to fit on it so I filed two of the flats down slightly so that I could put the adjustable wrench on it that I wanted to carry. I wrote up an alternative to a chain whip at this link:
http://www.bikeforums.net/touring/80...ip-travel.html

You do not have to get those cassette lock rings on that tight. Whether you use the Stein tool or the substitute chain whip I use, you should make sure that you can get the cassette off while you are still at home. But, you need to get them on tighter than hand tight.

Also the Stein tool or any other tool that uses the frame as part of the tool for leverage, you want to make sure you will not damage the frame when using it.