My car was running without a thermostat for a few months after I put in new spark plugs. The plugs are a bit fouled ( not horribly so ) and I was thinking about cleaning them. I've seen suggestions to use a wire brush and sand paper, but was wondering if just spraying them with carburetor cleaner and whipping them down would be sufficient?
Using carburetor cleaner should work just fine. I wouldn't use a wire brush or sand paper as these are abrasive. Depending on how much force you'd be using, you could actually damage the business end of the spark plug and limit its life expectancy. There used to be a spark plug cleaner which worked like a sand blaster, using compressed air and fine media to clean the spark plug off. I believe these have fallen out of favor, but even so, would require the purchase of specialty equipment to accomplish what you want to do. Your only other option is to just replace the plugs, but it sounds as though they aren't very old.
My RX7 was fouling plugs for a long time while we were getting the mixture settings right.
Use a small bit of wire to pull any solids out of the gap, and spray the inside with carb cleaner. Wipe it down and let it dry off a bit.
Then go and get a windproof lighter or a butane torch, and force the flame into the gap. There will probably be some sputtering and smoke, but you want to get the stuff out anyways.
After that, wipe the soot off, and it should work good as new.
Remember that sand blasting or otherwise scratching the porcelain of the spark plug will cause new deposits to cling easier to the spark plug. There was a period of time when new car manufacturers had the spark plug tips and porcelain, silicone coated to help keep soot deposits from clinging to the plugs. This was intended to alleviate problems with plug fouling between assembly line and customer delivery where most engine run times were minimal. The silicone fix didn't last forever but was effective for cars that never really got fully warmed up. You might try a bit of silicone spray (ArmorAll) on each plug. It was also determined that silicone could deactivate catalytic converters until burned off by running at high speed or after several WOT accels to 80 mph. Of course, that cleans the plugs, too. The propane torch trick for removing carbon is highly effective. Heat the tip until the ground electrode is at least red hot and you will see deposits glow. When cool, you can use a small pick or old tooth brush to remove the debris.