I followed the link and have tried The Dennis Technique, for a couple of hours. It is definetly an improvment, but still not good enough. If you see the examples in post #2 and #3 you can see the beautiful surface finish of those models.

Futhermore, my workflow is from Sketchup to Vue. In Vue I can add entourage as trees, ground and flowers etc, and do the mapping of textures (with bumpmap, specularity and so on). I have tried to use Piranesi. But the computer are not capable of rendering in  9000x6000 px size  Or even 6000x4500. If I try to use 'Render Area' and stich together several multipass renders Vue complains that "zDepth buffer (needed for Piranesi) is not compatible with Render Area". Moment 22. Anyhow I would prefer to work in Photoshop anyway.