Ive had a small amount of involvement in producing assets for a film in production. The film is called Zomblies.
For info about this film please visit http://www.zomblies.com/
This turret was textured using a combination of vraydirt maps in different slots, masking and various texture maps . The worn look was very quick to achieve compared to texturing manually.
Yes, thats pretty much it…with a combination of noise. I had to apply different versions of the dirtmap to the reflection and bump slot to get the right look, but vray made it much easier.