Don't know if this will help Brad. I had one plug hole that kind of did the same thing. I took my 1/2" copper tubing/fitting cleaning brush and cleaned the threads....but my fitting brush set is brass bristles.
Now you could go to the hdw store and buy those small parts cleaning brushes...they look a bit like over sized tooth brushes...they come in s/s bristle & fiber bristle & brass bristle....the ones that have the plastic hdls as you will need to trim it down so the brush end fits into the plug hole just right so you can clean the threads without the chance of the hdl part hitting any of the threads. Or if you are a marksman, your barrel cleaning brushes may work also. Ofcourse this whole thing depends upon the plug hole threads just being gunked up & not actually burred up. My one plug hole had some crud on the threads...don't know what it was...but my fitting brush fixed the issue, so obviously there were no burrs on the threads....just some anti-seize compound came back on the bristles which was my fault...now I use motor oil on the threads.
I don't know the thread size & pitch of our spark plugs, otherwise I would just say go get a chase....sorry!
Tom