I use this stuff
http://www.oneindustries.com/Detail.aspx?&pl=bikecosmetics&ft=ffffff&sh=900,900&catid=4&id=9170
Expect to pay around $30 in Aus shops. Can get it from most Motorcycle shops. Its really thick and when applied with a Heatgun/Hairdryer moulds great to all the curves of a crank arm and also Frames and sticks like hell. The frame Skin stuff is about 1/3 as thick.
I have it on my Cranks, Fork lowers, Frame, swing arm. the works.
I have it on Carbon Noir crank arms and after a season of racing I just removed it and renewed it for 2011 season. Crank arms look like new. It will even stop most stone chipping on frame down tubes.
I tend to do whatever it takes to keep my gear looking good. It costs Heaps and to abuse it would be to disrespect the effort and sacrifice my family has for my "hobby".