Rigged body in Cinema 4d

I don’t know if this belongs here, I’m sort of doing this for gmod and for other things.
After I rig the base mesh, how do I add stuff to it such as clothing, skins, armor, weapons etc. . . What other programs do I need and such?

I’m wondering the same question, is it possible to model for source in Cinema 4D?

I’m sure people could. One of the modeling programs listed on their Source wiki is Cinema 4D. I think you just need plugins.