If you want to go this one better, you can take a compression tester air chuck fitting and use it to keep the shish-kabob stick centered. Lacking a compression tester, you can break off the porcelain (flush with top of plug) from an old spark plug, chuck it in a vise, and using a pin punch, drive the old center electrode out leaving a hole just the right size for a shish-kabob stick. You will also have to remove the ground electrode (duckbill pliers, bend it back and forth until it snaps off)