I've used the Copperhill method on my 20D about 5 or 6 times. I ended up just using the blower method. I tried some silly stuff such as having someone hold a vacuum close whilst I was "blowing" - this probably just creates more dust movement
In any case, the blower method is safest and it removed the same amount of dirt as the copperhill method, but was much easier ofcourse. The copperhill method is simple, _but_ it is more risky becasue as you get more confident, you really start "scrubbing"
Cheers
Seb