I like the canned air that is just pressurized clean/filtered air with no oils or other additives: designed for sensor cleaning and such.  Rocket blowers can only blow what they "inhale": dirty, potentially humid air.  There's always the chance of sucking in dust particles and then accelerating them into the sensor/lens.

Mike

Gary-
The technique Mike and I talked about earlier is what you need to do.  Set the can on the table.  Give it a quick shot (to nowhere) to make sure there is no propellant.  Then do the mirror lockup and move the camera in front of the steady can.  That's what the camera techs do.  Practice a couple of shots on glass or a mirror to see that you have it figured out.

Seth

I'd be REALLY worried about blowing things apart with that.  I'd NEVER use it inside the camera.  Those cartridges are what are used to power hi-powered BB guns.

I have to admit that I kind of cringe when people suggest using canned air or otherwise pressurized air to clean a sensor. You don't have to be quite as paranoid about cleaning a sensor as one might think due to the fact that most cameras will have a filter mounted right over the top of the sensor that stays in place constantly.

However you do still need to be careful not to make the particles stick and to make sure that you're not scratching the filter. The main risk from the canned air is basically sandblasting and residue. As well as accidentally forcing particles into places in the body that they're not supposed to be.

If you're really, paranoid about dust, you can always get one of those portable clean rooms that are forthcoming. http://photipherals.com/?page_id=11

Cleaning the lenses themselves is largely another matter, you're mostly concerned about removing particles before wiping down the lens and with damaging the coating that most lenses these days have.

Turning off the camera is probably safer but I have done it both ways without negative results. I have access to Canon 500D, 80D and 7D2 and have done it both ways on all 3.
I try to be extremely  careful outdoors with wind and dust but I fear moisture getting trapped in the lens from the mount side far more. Fungus is death to a lens. Dust can be tolerated from functioning and image quality.

The camel hair brush is fine but keep clear of the mirror, most fragile part of your camera. Those first surface mirrors are extremely delicate. Advised not use anything other that clean air.