[RobertP]

I've cleaned my 20D 5 or 6 times now. Copperhill does the job and is cheap per clean once you have the eclipse and pec pads.

I have a rocket blower and if one or 2 bits of dust show themselves then that is often enough to sort them out. Sometimes a speck just does not move and then the only way is the wet method of copperhill. Usually a single swipe will shift it although once it took 6 repetitions to get it truely clean.

If you have a good light and good eyes you can see the dust when you look at the sensor. And remember you are cleaning a hard glass IR filter cover not the sensor.