Crumple a sheet of the sandpaper in your hand and dip into the wood paint. The color of the paint should be contrasting but still similar to the original color of the wood door.
Apply the paint-soaked sandpaper to the door in intermittent patterns. Primarily apply the paint to parts of the door that wear the most, such as around the door frame and near the door handle. Drag the sandpaper across the surface of the wood to give the familiar distressed look. Allow the paint to dry completely and sand over it with a new piece of sandpaper.
Finish the surface with varnish. Apply the wood varnish according to the manufacturer's directions and allow it to dry. Once dry, the door should have a rustic distressed appearance.