Tank Paint, with decals and scratches

Following the progress made in the rocks with materials post, I started to to develop a realistic paint for a tank modeling project that can be checked here. 

The node setup is here below:

Since the website where I got the texture from, had several maps of the texture already set up, it was easy to get a realistic result. 

One of the main ideas I had for the tank was to use decals on some specific parts of the texture. So, I  imported the front grill of the T-70 project, and tried to apply a decal to it. 

We start with the same base texture for the grill.

Then, use a ColorRamp and intensify the bumps with a Bump Node

Using a Simple ColorRamp we can create the Roughness Map to use on the Principled Shader

Then, we need to mix the decal, the scratches and the overall green texture

Decal base image

Decal With Separate RGB in Red

Scratches base image

Scratches ColorRamp output

Mixing Scratches with Red Channel from Decal

We have the following Node Setup:

That produces this result before the Principled Shader:

And after the Shader: