Render of vehicle and environment taken in 3ds max using Xoliul Shader 1.6. Snow effect added in Photoshop.
To save time, I did not add any high poly details, only chamfering the hard edges to create the normal map. Instead, I used nDo 2 to add panels, grooves and similar details.
After finishing the normal map, I used several different bakes including ambient occlusion (top-down and even), curvature (model-level and texture-level), world height to add a subtle gradient and world normal to add an upward bias to the lighting. This meant I was starting from an already very finished and consistent-looking texture. From here it was a simple matter of adding grunge (for which I used the curvature map to help) and other texture details.
For a bit of fun, I did a little animation and rendered it out as a video.
Here's the final model. This previewer hasn't quite got the speculars right, so it appears more like a black matte than the silver metal in the video/screens. (WebGL required)