Using a clean paper towel, wipe clean the stain. See if the stain is completely removed or not. If not, spray more hairspray and let is soak as before. To wipe clean the stain again, use a different paper towel because the first paper towel would have accumulated some of the permanent marker ink and will only make the stain worst if you used again.
If the stain does not go away with the hairspray method, try a different technique. Use rubbing alcohol as the cleaning material. Take a cotton ball and completely soak it in the rubbing alcohol. Gently rub the stain with the alcohol soaked cotton ball.
When repeating this step, remember to use a different cotton ball each time.
In case your car seats are made of leather, the best way to remove permanent marker stains is to use a small quantity of turpentine. When you are done blotting the stain, apply a small amount of turpentine on a lean piece of cloth or a paper towel and rub it on the stained area in gentle but firm strokes.