On Sat, 20 Mar 2010 09:36:23 -0700 (PDT), Joe wrote:

Wire brush leaves metal marks on the plug porcelain. Sure way to kill
the plug. Pros use glass bead blasting. Plugs are cheap, always good
to have a couple of spares on hand. When the engine revives, a fouled
plug can often be put back in and burned clean. If that fails,
discard.

I haven't seen a plug media blasting bag since the late sixties. They
worked wonders. A few pushes on the bottom and the plug was clean.
Then re-gap the plug and install for more miles. Eventually you had to
replace the plugs, though.