Does weathering work?
Weathering has been working. It causes “dirt” to appear on a model with opposing surfaces. This means that if you take a vase and weather it, you’ll get nothing or garbage. But, if you have two cylinders (like pipes), the opposing faces (the insides of the pipes that can “see” each other) will become dirtied. Weathering is normals aware. If you have them pointed wrong, it won’t work.