Photoshop: Create Grunge Brushes

This tutorial describes the way I use to create my grunge brushes. It's simple and easy, and something that everyone should be able to do without too much hassle.
All images used in this tutorial are copyright © Morgue File.

Step 1

This technique requires an image for it to work. When choosing an image, look out for old/grungy ones.

Step 2

Go to Image - Adjustments - Desaturate in order to make the picture black and white. Proceed to Image - Adjustments - Curves and make the settings something along the image below.

Step 3

Go to Image - Adjustments - Invert to invert the image and use either of the lasso tools to select the parts of the image you want to make into a brush. With the part selected, go to Edit - Define Brush and click OK. Make sure the background is white, or the brush won't become transparent.