Just showing how to paint Mudbox Lightspheres, similar to Zbrush's Matcaps.
To apply a litsphere : right click on an object > assign new material > litsphere material > browse to the image file.
To change the light orientation in the Mud scene, press down L and click-drag.
The video shows the process of creating a few spheres in Photoshop : Neutral, deep red with a rim light, and shiny.
It goes fast at almost 9x timelapse so don't try to look at the menus, just look at the spheres :P
Music credits :
Madonna - Lucky Star