You ever had your kids get into an art kit with markers or some bright colored lipstick that stains? Well, the same product that removes those stains from your walls will remove them from your kids as well. Just use a Magic Eraser! Permanent marker, lipstick, pen, etc. It will remove the stains from their hands and arms and legs (hehe) or anywhere else they may have written or smeared stuff on themselves. Trust me, out of desperation once I tried it and I've used it ever since.
So don't freak out when you're fixing to head out the door only to find that your little one got into a marker set while you had your back turned. Just clean them up and go :)