About to leave on a 3 week trip to a really dusty place. I was going to pack the sensor-cleaning kit I've used for 8 years with my 1D MkII, but I'm taking a new 5D MkIII as well. I don't know if the same cleaning tools would be bad for the 5D MkIII.
I use a cut-down rubber spatula wrapped in a Pec Pad, moistened with Eclipse fluid. It has done a great job with the 1D MkIII, but I don't know if the AA filter on the 5D MkIII is as durable, and if the gizmo that jiggles the sensor, or other sensor parts are easier to damage.
Yes, it is more sensitive, but more importantly the size of the IR filter is much larger than the 1D2. I don't know if it has the same thickness as in the 1Ds3, but that filter has been reported broken by several users (including a very experienced and careful friend of mine) because they applied a little bit too much pressure with their spatula.
What do people do with the 5DIII when it accumulates some junk that doesn't fall off by itself when the camera is turned on or off?
My workflow would be to first start with the least invasive method, a Rocket blower with (clean) air, followed by a sensor brush if needed. That will apply the minimum pressure, and should have a low risk of scratching. It also doesn't require chemicals, so it's safe to travel with. If that is not sufficient I'd use either a PecPad/spatula with a single drop of eclipse on both sides especially if there is oily residue involved.
Otherwise, I have excellent results with a LensPen/SensorPen, which also doesn't need chemicals. The LensPen gives me the cleanest results of all methods, and it seems like dust doesn't cling to the IR filter as readily anymore as it did before the treatment. Apparently it cleans extremely well, but do remove some of the excess graphite before (tapping it on a PecPad) and after use (sensor brush). But do not apply too much pressure, since it has a relatively small surface (which does allow it to reach the corners).
And as always, don't overdo it. Checking at f/22 is fine, but most dust will not be noticeable even at f/11 .