I stumbled upon a plug cleaner on US ebay and decided to give it a try.
Heres one of the offending plugs:

First I sloshed it in some wax and grease remover (prepsol) to try and get rid of some of the fuel/oil buildup so that the grit would not stick to it.
This is the cleaner I bought.

Whack the plug in the top.

The cleaner has a lever where you can open or close the grit, so I started with the grit off just to dry the wax and grease remover. Then I would open the grit lever and blast away for around 10 secs. Then turn off the grit again and blast to clean the grit away.
The result:

So maybe I'll have some plugs to try next time I foul one.
