Create your own collection of grunge brushes.
1. Creating Grunge brushes is actually a really simple task. First, open up a photo, preferably one that's pretty busy and has a lot of edges and lines. Once you've opened up the photo, Adjust the threshold of the picture by going Image>Adjustments>Threshold. Play around with the slider until you get something you think would work well for a grunge brush. Next, decide on the size you want the brush to be. I like working with large brushes, so I made a new document and made it 250*250 pixels. I then hit Ctrl+A (Mac: Command+A) to select the edited photo, and copied and pasted the it onto my new document. Below is what I have.
2. That could work already, but I like to go a little further by getting rid of all of the straight edges on the edges of the document. So, grab the Eraser Tool, and set the Mode to Pencil in the Options Bar. To make things easier, you may wish to enlarge your canvas a little so you can see the edges better. To do that, go Image>Canvas Size (you'll also what to make sure have white set as your background color before doing that). Now, use the Eraser Tool get rid of all the straight edges on the borders of the document. Once I quickly did that, my brush was complete.
3. Last, simply go Edit>Define Brush and give the brush a name. Now, your grunge brush should appear at the bottom of your Brushes Palette and be ready for use.
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