There is no “correct” way to finish mokume because there are many different ways you can finish this material.
We recommend starting by using a 800-1000 grit grind belt for a final finish, though you can choose to go higher. For a mirror-shiny finish, use a soft buffing compound after grinding. You can also buff out any scratches later.
Over time, the copper, brass, and nickel silver in your Mokume begin to oxidize and turn dark. If you want to get this look faster you can purchase different patinas that are designed for copper or brass.
Some people also choose to soak their piece for 1 to 2 minutes in ferric chloride mixed with distilled water, then neutralize the acid with a dip in a baking soda/distilled water bath for 3 minutes. When you remove your Mokume from the baking soda, simply wash it off with water and a clean rag. This will give you a matte finish with deep dark colors.