"Dust off" is also my first line of attract of crap on the sensor.
BUT, do not attempt while driving, under alcohol, etc.
Do this with lots of caution!
Just finished cleaning sensors on both bodies with Dust-Off, one needed a wet cleaning as the spots were round and looked as though they were "glued" on (this is the older 30D body with no sensor cleaning mechanism).
In an attempt to address the issue of the possibility of "freezing" or otherwise damaging the sensor, I tried longer blasts of perhaps one to two seconds long immediately after using several much shorter blasts to clean a sensor.
I then immediately directed the blast at my face. I was surprised at the temperature - while the top of the can became quite cool, the gas coming out was not cold - perhaps cool, but certainly no where near the temp where it could harm anything. Even blasting continuously for several seconds did not cause the gas to become cold.
I'm convinced that the fear of freezing or damaging the sensor or any part of the camera is completely baseless. And there are no new spots from the refrigerant gas.
I'm seriously wondering if the conventional wisdom wasn't based on someone's hypothesis and it gained an internet life of its own when no one questioned it. On the face of it (cold temperatures, propellant contamination) seem somewhat logical - but then so did Aristotle's theories for two thousand years.