just a guess, cause I don't actually know much about this stuff; but Kanthal is designed to form a layer of Aluminum Oxide on it's surface when heated: specifically to impede conductivity across/beyond the surface of the wire. As one initially glows a new coil, the Aluminum Oxide layer forms during the first couple pulses, and the coil loops won't short out against one another after that. However, if one is employing a tightly stacked, contact, micro coil, yada, then there are places where the wire is coming in contact (with the neighboring loop) tightly enough that the Oxide layer doesn't form well. Brushing after the initial pulse breaks these contact points and allows the Oxide layer to form there as well (which is, obviously, also the point where it is/was shorting out).