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This actually works very well on some skis. There's a reason K2 went to beveled top edges on their twintips in the last couple of years.
I know someone who did it on a belt in the workshop, not exactly sure which way they went about it.
If you had your bindings off you could use a plunge router, they have specific bevelling bits. This would give you the cleanest, nicest finish, just be aware that 1 slip with a router will make a HUGE mess.
Otherwise, if you just want a slight bevel, a coarse file or some sandpaper ought to work fine.