This grunge Photoshop brushes from Creative Nerds might suffice if you’re seeking a rough paint stroke. They’re high-resolution and free to download, and they’re suitable for both personal and commercial usage. To get access to them, you’ll need to sign up for Creative Nerds (which is free).
Creative Nerds was in charge of the design.
Usage: Personal and commercial use are both free.
Rough paint strokes brushes are available for download from Creative Nerds.