1. Make a blank image no more than 255 by 255.

2. Draw whatever you want on that image that you want your brush. It doesn't matter what color it's in, although it's probably best if it's in black.

3. Select the entire image.

4. Click on the Airbrush tool.

5. Go to the Tool Options window. Click on the Brush Types button that looks like a tiny paintbrush.

6. Click Custom then click Create. And you have your own custom brush! Sometimes it messes up and you have to create it again.