Check out Spartan Worn Cerakote. You can do the same thing w regular paints. Use a bronze, distress with black and then highlight recesses w a Tiffany/Robin’s Egg Blue and distress down again. Use fine sandpaper or a scotch brite. Like all techniques, be sure to practice a couple times. It’s not difficult. Using paint is different that Cerakote you may want to clear between, or allow the paint to fully cure between colors, maybe partially cure... you’ll have to experiment.
Looks similar to one I just did! Lol! I used an Aqualac metallic silver base like @NotSoFast mentioned and a satin topcoat rather than matte. Gives it just a touch of that sparkle. And Satin Aluminum Cerakote on the barrel.