If you think your ready, then proceed.

Step 1.
Open a grunge signature or grunge Background, ill be using this one:


Step 2. Create a new color balance:


Step 3. Adjust the color to what you want by sliding the bars in the Color Balnce, Then click ok.
Next, get a grunge brush and make sure your color is black(Press "D").

Now click on the image a few times. You will notice a few parts will lose color, this is whats supposed to happen.


Step 4.Now create another color balance:


Step 5. Now it should look something like this depending on your colors:


Now simply add your render, blend, and add any other effects. Heres what i got from the end result:



Hope this helped some of you :-D