Hi Red,
well i'm not a C4D user but i think the technique would be the same. Try unwrping the uvs and the paint your decals in a 2d software like photoshop. If u've not heard about that, Its called UVW UNWRAPING. Here you flatten out your geometry to a 2d plane image and then paint in your textures.
I searched a video for you to get started. Check it out here. Or if you are not satisfied then google up some tutorials on it.
I use MAX and there is an easier way to do this. Its called COMPOSITE MAPPING. I dont know about C4D but you can google up the same for C4D. I'm sure ull get desired results.
Best of luck!!!!
Memory 4gb
Graphics Card ati 6550
Monitor Setup sony full hd
OS windows 7