Burnishing Graphite into Outside Hub

I haven't read of anyone else doing this, but we have been using the eraser from a mechanical pencil to burnish graphite into the outside hub for the past 3 years. I assume it works since we haven't noticed any problems from doing it. I just had a thought that maybe there could be residue from the eraser being left on the wheel? Would the end of a polished pin gauge be better as long as it's not pressed too hard into the hub?