I’ve been following this tutorial: http://cgcookie.com/blender/2011/07/12/creating-a-grungy-brick-wall/ and it’s been very helpful to me to create a realistic wall. The only problem is, whenever I try to paint on the wall, it doesn’t work. I created a new UV image, standard black, and saved it to a PNG file. I opened that PNG file into a texture on my wall object, but then the complete wall just gets black. How can I fix this so the correct wall color remains but I will be able to paint on it?
to texture paint on an image, it must be joined to your UV coordinates in the UV window. then you go into texture paint mode in the 3D window, and you should be able to see the texture in both solid and textures draw mode. you can also go into texture paint mode in the UV window.
Hmm, it seems that over the last days I’ve gotten more and more lost in my problem. I’m attaching the blend file I’ve been editing. Whenever you turn on the graffiti texture on the bricks object you’ll see what I mean. I have absolutely no clue how I could just have a texture I can paint on that doesn’t get repeated and doesn’t show the gray or black or whatever color the graffiti image standard is. I hope somebody can explain what I did wrong and what I can do to fix it. Your help is really appreciated here 
Thanks in advance
Note: Somehow uploading the file here didn’t work so here’s a link: http://www.mediafire.com/?0ibqrxl9uuero72.
I’ve been struggling with this problem for quite some time now and I would really appreciate it if anyone could help me with it