Do you mean the Urban Decay 24/7 eyeliner pencil or the shadow pencil? I think both are pretty easy to sharpen.
I supoose you could depot it but I am not sure why you would want to if it was a pencil eyeliner.
I am uncertain as to how (or why) you would want to do this. But... I suppose you could break off the tip, place it into a small container, sharpen it, and continue that process until the pencil is down to a stub. Once you have a suffient amount of pieces broken off you could smash them and they'd be like a pot liner you would apply with a brush. I am uncertain how the quality of that would be however.