To restore a front door, we removed it from its hinges. It's much easier to work on it while it's not hanging.
We used Klean-Strip KS-3 Premium stripper to start. It removes varnish, oiled based paints & latex paints. Use rubber gloves to protect your hands & paint on with a standard paint brush. Allow the product to sit for 15 minutes.
Use a scraper {preferably plastic}, remove the paint.
Next, we clean the door and allowed it to dry.
Using a hand sander, lightly sand the door to reveal a fresh layer of wood
Use tung oil or a clear, matte varnish to give the door some protection. You will still experience some weathering with tung oil if the door is exposed.