Step 4: Sand the Exterior Door Paint
One of the most important preparation steps in this DIY project is sanding all the surfaces of your front door before you begin painting.
But before you start sanding away, be sure to select the sandpaper that will work best with the paint that was last applied to your door.
If you do not know whether your existing front door paint is oil-based or water-based, use this easy trick to find out: Dab some denatured alcohol* onto a cotton ball and then rub it on the door. If the paint comes off, it’s water-based. If it doesn’t, it’s oil-based.
If your front door paint is water-based, give it a good sanding with a fine-grit sandpaper. For oil-based front door paint, a medium-grit sandpaper (100- to 150-grit) will do the trick.
*Note: Denatured alcohol is not the same as rubbing alcohol. Look for it at home-improvement stores.