What's it about?
No matter how complex the geometry, the program can "map" a texture onto it from a flat image. This suggests you might "unwrap" that relationship, recovering the 2D raster image that (somehow) ends up on the object. You could then take that 2D image into Photoshop (or whatever) and edit it in such a way as to get the results you're after. Even better would be "Photoshop-like" tools (airbrush, etc) that could be applied within the modeling application to let you define arbiratray textures while modeling.
While some applications (including form-Z) include the option to "unwrap" a texture into a file (called uv-mapping in form-z), it requires specialized software to do the "paint in 3d" sorts of things.
Last updated: April, 2014