Jerry Kitts suggested using Dr. Martin’s inks for staining ties a while back. I decided to try to use the Sepia ink mixed with Isopropyl Alcohol (IPA) on a pair of San Juan Car Company double truss trucks. The truck was painted with a color similar to Floquil Weathered Black. I let the acrylic paint sit for a few days to ensure it was hardened.
It is a good base to add other highlights such as oil around the journals. The ink dries and leaves a residual grit on the truck. To my eye, it does add a 3D look to the grime and dirt that accumulates on the wheel faces. Journals tend to lead oil and creates a “magnet” for dust and dirt.