Pasting a seperate image into UV Wrap

[defaultchg2c2crn953]

So I'm working on a design for a gun, the AWP in CSGO. I did a rough sketch in a separate UV document and copy-pasted that layer onto the actual UV unwrap from photoshop. Pasting the image I painted into the actual UV map did nothing but drawing on it still works even though it appears to be the same layer. 

[Trevor.Dennis]

Our @davescm  is probably your best chance of getting this answered

[JJMack]

How did you create the layers so the gun surface textures filled the matching triangle UV  surface areas correctly. You 3D gun model seems well create still the surface UV would be hard to fill in. with appropriate content.  I have only tried simple geometric solid models. I create Collages templates or mockup templates for the models uv surface areas and populated the template with image content. Then I drag the collages layers into the model's surfaces psd document.