Texture painting - POC

Proof of concept - weathering an object in Blender/Cycles by using a composite material with hand painted mask/opacity textures and AO bake pass for dirt mask.

Texture resources used:
http://texturelib.com/texture/?path=/Textures/metal/bare/metal_bare_0029
http://texturelib.com/texture/?path=/Textures/rust/completely%20rusted/rust_completely_rusted_0049
http://texturelib.com/texture/?path=/Textures/plastic/plastic_0032