Re: adding thickness to mass
Either a model in place or family, you don't need to create the thickness. You can convert faces to walls. If Revit complains about not being able to make a wall out of a certain surface, you can try subdividing the form, and try again. By looking at the image, there seems to be lot of self intersecting geometry that might not work in one single piece. Consider making smaller pieces that can be interpreted in a better way by the Wall by Face tool, or simplifying the design.