Here’s a brass/bronze test piece that I made look like rusted steel by super gluing steel powder to it, then it was rusted using salt and 20% hydrogen peroxide. After rusting, the darker right side was q-tipped with pure tung oil and allowed to dry for two days, to simulate rusty steel that’s frequently touched by hands.
If you use this technique on the dog tags, use super glue with a longer drying time to give yourself plenty of time to dust it with the steel powder. 10-second-cure glue is what I had on hand, and you can see that I missed some spots because the glue dried too quickly where it was spread thinly.