If you are going to use scourer pads you need to put them in from the front of the muffler, not the back, so they will get blown through until they hit the first baffle. If it is a full-width perforated baffle, they may stay there. If it is a part-baffle, of course they will end up coming out of the exhaust pipe if you open the throttle a few times. However, The Man might be off your back by then, so the problem is solved.
In my indiscreet youth I once needed to get a home-made car registered, and at that time you had to take it to the police inspection station for examination. I put long rolls of flywire, fairly tightly rolled, into both exhaust pipes. It still wasn't quiet, but the cop sort of gritted his teeth and tolerated it. Then I used a long wire with a hook in the end. Fortunately, the world has become more civilised since I was a lad. I hate loud exhausts now.
