1. If the paint is still fresh, scrape off any excess with a knife or other utensil.
2. Dab the stained area with a towel soaked in warm water.
3. Soak the denim in isopropyl rubbing alcohol (something you should definitely keep on hand for first aid, cleaning electronics, and, yep, laundry).
4. Rub the fabric against itself, and then scrub it with a cleaning brush or toothbrush against the grain of the fabric, lifting as much of the paint off as possible.
5. Rinse the stain in warm water.
6. Toss the jeans in the washing machine, and wash alone in hot water.
In a pinch, you can also use dish soap, hand sanitizer, or hair spray. (The alcohol content in the latter two options helps break up the paint.)
