My recommendation is to use a Dremel tool. They are sold in kits with an assortment of burrs. I would use a small carbide burr to shape the metal, followed with a fine abrasive-embedded rubber conical bur to smooth and polish. Then after degreasing with Dawn detergent and hot water, dry and spray with flat black paint.
Disclaimer: Wear eye protection. Clamp the plate securely. Let the tool do the work (don\'t rush or push hard).
Here\'s an example of a Dremel kit. They are often on sale (Black Friday?) and I bought this kit for about $59.
