Render and isolate elements of the machine
Still in KeyShot, I render out a 2,000 pixel-wide .tif with Depth and Clown Pass checked. In Photoshop I open and then copy and paste the passes on to the rendered image. I set about using the Clown Pass to help select with the Magic Wand, and copy and paste rendered elements. Isolating them enables me to apply Adjustment layers, and lift and modify the black point on each part.