This tutorial will cover the grunge effect that I frequently apply to my digital creations. There is often a debate on just what grunge is, as some artists hold different definitions of the style itself. For the purpose of this tutorial, and the definition that I hold true, grunge will be the application of dirt-like components to your images.
The most important part of this tutorial is not for you to learn the technical accuracy of the steps below, but to understand that grunge should never become the image. By that, I mean that you should not use grunge in your work to the point that it becomes the focal point. Grunge should always be used to compliment your composition, not take it over completely. With that said, let's get going...
Option 1: The brush
First, you will need Photoshop brushes, possibly some new ones. I have found that the best source for Photoshop brushes is: VBrush or Brusheezy. There, you will find more Photoshop brushes than you could possibly use. I have used this site numerous times and consider it a valuable designer's resource. Listed on his site are instructions on installing your new brushes.
For my example below, I am using brushes from Nocturna. Given the nature of this tutorial, you will find it purely textual. Grunge is best left to the creativity of the artist, this is simply a means of facilitating that creativity.
Feel free to download the image and use it for this tutorial. The next step, is to create a new layer. Press Shift + Control + N, type in black grunge and click OK. Now you have a new layer to work with your grunge. This is more of a personal preference than anything else, however, I have found that by seperating the layers, I have more control and ease of editing.
Press "D" to make sure your foreground color is set to black, select the brush tool, and select your grunge brush by using the Options toolbar. Now, click throughout your image where you wish to place the dirt. Adding grunge is as simple as that. However, the question I receive all the time is how do I do it?
To answer that, I use the above steps, but I also experiement. Experimentation is key with grunge. Not only try a black grunge layer, but white, or other various colors. Disquise your brushes, or make your own (I have another tutorial for creating your own custom brushes). If you apply a large brush, try using your eraser tool, with a different brush selected, to remove portions of the grunge you just applied.
Try different brushes, VBrush has plenty for you to experiment with.
Option 2: The photo
Another method I have used to add grunge elements to my work, has been actual photographs themselves (If you need some textures to work with, please visit my resource section and download some stock photographs to work with). Simply stated, bring the photo in and change the blending mode to Overlay.
From there, apply the methods mentioned in option 1. Grab the eraser tool and a grunge brush, and selectively erase portions of the new textured layer, revealing sparatic portions below it. One of my favorite brush resources for this has always been Jeff's Digital.
That is basically it. For some reason, the technique is believed to be much more difficult. I am sure there are other methods that other artists use, however, these are what I have found to be the easiest.