I've now got to a stage were I'm happy with the 3D model and texture of the X-15. Now for the 'Devil in the detail' part, adding the rivets and other surface details. When I've added all these on the texture file, as a separate layer, I'll create the Bump/Normal Map to give an added effect to the 3D model.
I've been looking for a way I can easily add the rivets and surface details on to the texture file. The best way I have found so far, is to use Inkscape to add lines where the rivets are, then change the style of the line to dotted. Then import the texture file in Wings3D, check it, and then return to Inkscape to make any changes and re import if required. So I've been swapping between Inkscape and Wings3D all morning. Multi Monitors are very useful. think I get two large widescreens monitor after this is done!