Here is how i built up the Mini gun texture slowly adding textures as i go and at the same time i tend to do a quick render back in 3DS Max to ensure that the new pieces of texture applied look OK when rendered out.
I wanted all my model to have a similar theme and look so whilst creating my textures i had to ensure that i was keeping consistent with the Assault rifle.
Whilst creating the Mini Gun texture i managed to hold of a copy of V-Ray a renderer i had seen people use on the Internet. I wanted to experiment with V-Ray because in the back of mind i was thinking ahead and about when i come to doing my final renders of the models. It was interesting to see how V-Ray worked i liked the way the shadows where cast in the scenes, however i was not sure if i would use V-Ray as a final renderer or not.