Automatic Transmission oil down the carb with the engine running helps some as well. Your neighbors won't care for the smoke cloud however. I would go with the Sea Foam or MM as suggested by Kwai.
I have a spark plug blasting box that cleans them up real well. I used to use a wire wheel in the drill press on slow to clean the Mini plugs back when I was in High School. It was good for 2 maybe 3 cleanings before the plugs just didn't work anymore.
Spark plugs don't like cold fuel rich running. Getting a I6 engine to be warm in all cylinders is a tough job with it going down the road. Starting, moving and turning it off just kills plugs. I had a '37 Packard 120 coupe I had a 283 in. I was running my own restoration/used car lot at the time and couldn't work on the car if paying customers had stuff in the shop. I got it to driving itself around and just moved it around for weeks on end until I could work on it again. 3 weeks of daily starting, moving, turning off, repeating each evening and morning was about all a set of plugs could handle. I got to where any plugs that were on sale at the parts house no matter the rating or heat range were what I bought just to keep it mobile.