Crumple the sandpaper in your hand and dip it in the wood paint. The wood paint should be a contrasting color from the paint already on the door. Crumpling the sandpaper helps give the artificial distressing a believable, rustic look.
Dab the sandpaper over the pine door. Focus on parts of the door that typically see the most wear and tear, such as around the doorknob, down near the kickplate and near the hinges. Allow the paint to dry completely before sanding the door to give a uniform texture.
Seal the door with varnish. Apply the varnish according to the labeled instructions and allow it to dry completely. After drying, the door should have a pleasant, rustic, distressed look. This process can be repeated to enhance the distressed look of the door.