One of Photoshop's neat features is the ability to add custom brushes for image editing. While there are plenty of places to find those online, you can also make your own.
Photoshop guru Helen Bradley runs through the steps to make your own custom brushes in Photoshop. The key requirement is a high-quality image with an interesting element you want to use for painting, and the usual patience for tweaking minor details that's a hallmark of everything in Photoshop. Hit the link for the full details of the process.
Make Your Own Photoshop Brushes [Project Woman]