Rub down with Magic Erasers, or the lighter/wet paper towel method to remove the oxidation. Make a paste of water and Barkeeper's Friend, apply to stem and let dry. Thumb buff the Barkeeper's Friend off and rinse with water and dry. Apply a small dot of plain white toothpaste such as Colgate to your thumb and evenly coat the stem. Allow to dry a bit, 30+ minutes, and thumb buff until gone. The toothpaste may need 2-3 applications, but more often than not, one application suffices.Teach me your secrets.
Gotcha. I just use my thumb with the Barkeeper's Friend and toothpaste. No oil necessary afterwards.^chasingembers, that's why I finish with Obsidian oil, as directed on the bottle. I've never had my stems turn out with a matte finish. Perhaps you aren't buffing them enough after using the Flitz. I wipe vigorously using polo shirt material rags. Perhaps you might try using a microfiber cloth to buff off the Flitz? Hope you have better luck.