Christopher,
I had a CAT gasoline forklift at work that had a bum cylinder. It fouled that plug daily. A small wire brush and some carburetor cleaner allowed me to clean the plug suffeciently to run it again for another day.
When lead was an additive in gas, I have fouled plugs and come hell or high water, have not been able to clean them well enough to fire again.
If you happen to have a small blast cabinet set up with glass beads, you could use it to clean the plugs, otherwise, light oil and soot can easily be taken care of with a wire brush and some type of carburetor or brake cleaner.
Stuart
