Here's a screenshot of the settings for the top right shader, as requested. Control your dirt colour with Blender 3. Control your metal colour with Blender 4. The spread of the dirt is controlled with value 2 of Math Functions 5 (up for wider dirt, down for narrower dirt). Math Functions 3 controls the roughness of the edges of the dirt. Change both values at the same time, but keep value 1 exactly 1 higher than value 2. Notice the granite node feeding into Math Functions 4? For dirt like the top left ball in post 22, feed a turbulence node into Math Functions 4 instead (leave the granite node alone for the other things it drives). You'll need to adjust the scale settings of the turbulence node when you do that. I'll answer a few questions in a mo.

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