Heck even if you are gonna sharp it on a drill grinder, if some fool has badly mangled it I think it is quicker to whip it into shape by hand, then shine it up purty on the drill grinder :-). I have done large drills on a belt sander :-) or a disk sander :-).
Knowing how to hand gash an endmill is a nice skill to have too :-)....takes the same kind of a steady hand.
Bill