The strange bit comes when the duster reaches a cheekbone. Your ear's natural defence mechanisms will take over and the muscles inside will tighten up, with consequences on what you hear. It should work with both ears. It's quite possible to trigger these muscles voluntarily and sometimes they contract involuntarily, especially when you're expecting to hear a loud noise. However, unless you're thinking about it really hard, this is a way to make them contract.
Try it! I'd love to know whether you find the same or whether I'm being more of an alien than usual. (Perhaps it only works if you're naturally tickly in the first place.)
Could there be a bid for an Ig Nobel prize in this?