"Most everyone I know of, incl
"Most everyone I know of, including myself, uses mineral spirits.
Core plugs.... Keep in mind that under those core plugs are passageways with a floor so to speak. You do not want to poke anything too deep thru the plugs as that might damage the carburetor.
I use a center punch to cave the core plug in somewhat. Sopmetimes that's enough and the plugs is loose enough to shake out. If not, tap a sharp pointed scribe thru that indented center punch mark just far enough to pry it out."