Yeah, I've done one ledge and I didn't find that wax did much.  Just get a big chunk of crusty snow and spread the little ice chunks over it, like a little here and there.  Also, running an old ski or your friend's ski (when he's not looking) over the length of the ledge a bunch of times grinds out a lot of the roughness (at least on the ledge I did).  Either that or you can catch an edge and die or stick to metal.  Hope that helped.
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Line Skis, Adidas Eyewear, Fanatics, East Cost Alliance, Teem Bousquet