Gray Detail Mask Overlay In 3D Space

Hey guys, trying to learn how to do Anime Cellshade in Unreal since many games (FighterZ, Guilty Gear) was made in Unreal. I studied the models and materials best I could but one thing I am having trouble recreating is their Gray detail mask. There are flat planes over skin or meshes of characters and are always over a base gray mask.

Trying to figure out how I am supposed to overlay the gray to the world with some sort of overlay shader. The detail map seems to be default gray and in photoshop if I was to use an “Overlay” the grey outright blends, not interacting with any pixels in any meaningful manner.

Any other colors will get overlayed with the colors behind it. I am trying to replicate this in a shader. Does anyone have any tips or examples I can look at? I’ve been trying to google it for a while now but cannot find exactly what I want for the life of me. I tried using decal shaders but since the cell shading is Unlit it doesn’t overlay ontop of it.

Hopefully you don’t need pictures but if required let me know.

Hello KuroKairaku,
I’m not really getting what you’re trying to accomplish. I think it’d be helpful, if you could share some pictures with us.