How do I add grunge & rusting texture to a pre-made material? [CYCLE] I am working on a nature scene where there is a car due to nature it gets rusted and rather by time it gets old. I want to add grunge and rust texture. I had bought materials plugin a while ago, so used the already made plugins from there. The problem is I have no clue where to apply the roughness texture since I am not that experienced.

Firstly, the grunge and rust textures are from megascan ( not sure if this helps).

First the glass material;

When you expand it this is what it looks like


Where do I apply the image texture of grunges which I got fro megascans to , where do I plug it to be exactly?

Second

I also have another metal material which has scratches over it, and it is premade, I would like to add some rust texture as well from megascans.



I can probably post the whole node, but I don't have 10 rep.
You mix nodes with Mix SHADERS use "fac" to blend between both influences. And then connect that last node to the Material output.

Here´s a 4 minute vid on how to make rust: https://youtu.be/hccqcCIGGUw
When you're done, connect it to the second plug on your mix node (the first one is your glass shader).