Hey guys, I found 10 packs of grungy Photoshop brushes which are nicely made. What you can do it load the brush presets into Photoshop, create a document with an alpha background, and use the brush to create a document sized piece of grunge which has an alpha behind it. Then you can save that out and load it into Cinema 4D and use it in the alpha channel of a material to put grunge on your object. I show you how to do that in this tutorial: http://www.thepixellab.net/cinema-4d-201-tutorial-adding-grunge-to-objects Enjoy the free brushes!
7. Coffee Rings