Here's a tutorial for making a classic swirl brush.
1. Open Adobe Photoshop and open a new image with a transparent background (around size 120 by 120)
2. Click on the type tool (it's a giant 'T')
3. Type in a capital Y (color: #CCCCCC), change the size to 100 and change the font to a cursive-y style. (I used Script MT Bold)
4. Drag the Y to the right-hand edge so only half the Y is showing
5. If your layers palette isn't open, go to Window- Show Layers and click. Then go down to the layers panel and right click on the word Y on the layer. Click on rasterize layer.
6. Go to Edit- Stroke and click. Change the width to 3, color to black, and location to outside. Press ok. Go to the layers panel again and change the opacity to 70%.
7. Go to Edit- Define Brush and click ok. Done!
Note: this brush can only be used on the right side of images. If you want a brush for the other sides, go to Edit- Transform.

NOTE: There are other ways to make a swirl brush, but this is the most common way. You'll get the best results if you use a very thin cursive font.