Deburring is essentially what we're trying to achieve, just picture your burr as being sharp edge and not something which stands proud.
You want to work the edge so as to round it off rather than flatten it, so I'd recommend giving it a couple so strokes at 45 degrees to each face (assuming it's a 90 degree edge), feel what's happened, and then work more aligned with each face in turn to deform the material equally and roll the edge.
Try on a piece of scrap metal first, an old piece of cutlery is good, and try not to apply too much force to speed the process up as if you slip, the point may scratch the case badly.