Exporting multiple materials to a single diffuse/specular map

Support Materials and Textures
1

I created a low poly scooter and applied different materials to different parts of the mesh for obvious reasons (check the photo below).

New Bitmap Image.jpg1440×900 305 KB

There are two things I need to do :

  1. I want to put all the color from my multiple materials onto a single material or onto the UV map (whichever is easier) so I can export a single diffuse texture.
  2. I want to create a specular map based on my materials so that the metal parts look shiny and the other parts don’t.
    What is the best or easiest way to do it?