Firmly in the holiday spirit, NitroMan has released a free tool in MagicDraw for Cinema 4D, which will allow you to quickly and easily paint materials on object.
With MagicDraw, you can paint directly on a selected object in the viewport, and by switching materials, MagicDraw provides a nifty workflow for applying multiple shaders onto the same object in C4D in specified places.
Magic Draw plugin allows you to paint your objects with materials
MagicDraw paints directly on the objects faces and has a multi-object feature, which will allow you to paint on multiple objects having them act as one continuous surface. MagicDraw can also quickly paint on an entire loop in a model, and has some controls for brush size and type of brush. Check out MagicDraw for Cinema 4D here.