I changed a few things here and there, mainly i moved some of the nodes, especially the color nodes out of the dirt generator.
I like it this way more, because I think mixing the roughness maps and colors within the dirt generator is a bit too much abstraction. I think generating a height and roughness map alongside outputting the dirt mask works well, because you have the most flexibility to continue working with the dirt generator output. I also wanted to be able to completely change the plastic roughness, normal and diffuse map, so I chose to handle the mixing parts outside of the dirt generator, using the outputs I named earlier.
Here is what I came up with for my dirt generator:
And this is how I am using it:
I also changed the dirt thickness and density slider handling as already shown In this thread. I also used a map range node to smoothen the dirt heights within the generator instead.
Cheers,