I want to paint moss and rust (etc) onto various objects in my scene. See below. The mesh is too spread out on the UV Map therefore Photoshopping directly is not possible. Since you are able to paint color onto the object I was wondering if there is a way to directly apply a texture onto an existing UV-Map in the same manner as seen in the screenshot below.
The only other alternative I see would be to Export the UV result (left picture below) into photoshop and use the orange color as an Alpha filter for an additional texture such as Moss. It would be painfully complicated and slow and there would be visible seams around edges that are Split by the UV unwrap.