Control albedo color overlay with a texture mask?

Artist needing assistance. My goal is to have a material / shader which allows me to set a custom paint color on a set of props that I am creating. Simple RGB input to control this color. This custom color must to be limited to the "paint" area of the texture. I want to control the opacity of the overlay with a texture mask (below) so that it does not affect the underlying metal exposed by scratches or the overlaying grime and rust. The color should act like a Photoshop Blend Mode, tinting the underlying texture color.

Here is an image of one of the props:


Here is the base texture:


Here is the texture for the color mask:


I was able to get this working in Unreal Engine using a LERP, RGB input and Blend Overlay. No luck as of yet finding a method in Unity. I'm OK at working with nodes... but scripts aren't my thing!

Thanks in advance!

 

You can get shader forge from the asset store which is an Unreal like shader editor.

https://www.assetstore.unity3d.com/en/#!/content/14147

 

Thanks, I'll check this out.