When applying sunscreen, you want to make sure you cover every inch of your exposed flesh to protect yourself from sunburn and skin cancer. If you apply lotion when you're already dressed, you tend to miss spots since you want to avoid getting lotion on your clothes. I highly suggest applying sunscreen before dressing, to ensure that every part of your body, neck and feet included, is protected. Not only will you be fully protected from the sun's harmful rays, but you'll also avoid those bizarre streaky blotches on your skin that you get when you accidentally overlook certain spots. Remember it takes an ounce to cover your body completely. For a visual reference, that is about the size of a shot glass.