I'll have to state that I quite liked using a modification to a "simple" charm to defeat Dumbles. I somehow doubt that anyone but a muggle-born or muggle-raised would've thought of that particular approach since Purebloods seem pretty ignorant of basic chemistry and physics.
Now, the one approach that'd be good for near-slapstick in taking Dumbles down would be to hit Dumbles with a Barba Maxima spell and give him a beard so long he keeps stumbling and tripping on it.