Unfortunately, 'select all with same material' doesn't seem to work on undefined or default faces -- that is, at least as of Sketchup 8, which is the version I currently use. (Although I'm not exactly sure why that is. I seem to recall the free version of Sketchup 8 includes certain functionality that subsequently exists only in the Pro versions of later releases -- but it's been so long since I had to decide which version to use, I don't recall the details.)
For use with SH3D, watch out for size.
I quite cheerfully ignore Emmanuel's no doubt sage advice regarding the sizes of both models and textures. Undoubtedly by doing so I only make things more difficult and less reliable -- but I find it nearly impossible to create photo-realistic images otherwise. (Not that SH3D was originally intended to be used to create photo-realistic images -- but it does such a good job of it so easily, I can't help myself.
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