Correct, don't use canned air as it has propellants that will fog up the sensor over time. In fact, one client of mine used to use canned air all the time to clean his camera and lenses untill his images started to get very soft. I went through several pec-pads tying to clean all the gunk off of his camera and lens...

If you do need to blow air, then make sure you do so with a pure
CO2 blower (one without oils) or a hand-pump blower of some sort.

I've always done the customized spatula and pec-pad method. Petteri has an article regarding the Visidust that's worth a look.

Any suggestions on the best way to clean a sensor on a Canon 20D.
I have been told not to use compressed air, it this right?

What about the visabledust brush?

I scratched my sensor with the spatula and pec pad method and now use sensor brushes and find that these are highly effective and quite safe.  Michael used to recommend pec pad and Eclipse fluid until he tested sensor brushes.