that will do nothing to clean it out... we do this with glass packs and fart can ( big chrome can mufflers) spray agood carb cleaner or even zippo fluid in them, let it soat in for amin sqirt more in and make a trail from the tip to the ground away from muffler so you can light it.... it helps break up the packing to make them louder..
also do somehting simmaler with oil.. get some cheap two stroke oil, and pour it into the muffler than lat it it and soack in before you instal lit on the car/ truck, it will smoke for aday or so but will burn the packing up quick