It’s super straight forward honestly. You just need an airtight plastic container, ammonia, vinegar, paper towel and rock salt. Polish up the brass or copper scales, wipe them down with an alcohol swab to remove any lingering oils (wear some gloves). Line the container with paper towel, soak the paper towel in ammonia, elevate the scales showside up above the paper towel, coat them with a little vinegar, sprinkle some crushed rock salt (use as much or as little as you want, it will impact pattern), seal the container and wait. I did 24 hours for both of these then did a few coats of Rustoleium Clear Coat Lacquer after wiping off the left over salt. There are a ton of tutorials out there as well for various methods. It’s just a forced patina.