If you do anymore, you'll end up like I ended up ........ I cleaned the complete black off the plate.
If you want that, use thinner on it. Paint guys sell what they call a special thinner. Its basically a slow thinner that doesn't evaporate as fast and sits in the paint, allowing the paint to lift up a bit. A few tight scrubs and the paint comes off.
If that doesn't work, take a # 1000 or 1500 sandpaper and do a wet job on it. i.e. let the sandpaper stay in water for a couple of hours and then scrub the it on the complete plate, often wetting the paper and plate.
Using a high # paper doesn't leave streaks on the metal.