1. Prepare the surface
To reveal the wood's figure and luster, handplane the surface and follow with a card scraper in any torn-out areas. Then sand using P220-grit paper, paying particular attention to end grain and sharp corners, but avoiding large surfaces planed and scraped.
Wipe the whole piece with a damp cloth to raise the grain. Then lightly sand the wood with 400-grit paper (CAMI). Finally, polish the whole surface with either a gray abrasive pad or 0000 steel wool. This allows the oil applied next to penetrate more evenly and reduces the chances of blotching.
Flood the surface with boiled linseed oil and wipe it around with a cotton cloth. Allow the oil to penetrate the wood for an hour and then wipe the surface dry with a clean cloth. Spread the used cloths outside to dry before disposing of them to avoid the risk of spontaneous combustion. Wait two days, and then apply more oil in the same way as the first time. If any areas are still absorbing oil, wait two days and apply a third coat of oil.
3. Apply varnish washcoat
When the oil is dry, apply a coat of thinned varnish with a foam brush. Use one part varnish and three parts mineral spirits. Let the washcoat dry and then sand it with 220-grit sandpaper.
4. Apply first coat of wiping varnish
Next, make a wiping varnish by combining one part varnish with one part mineral spirits. Apply with a foam brush and let dry. Sand with 220-grit sandpaper.
5. Apply two more coats
After the last coat of oil has dried for two days, rub the surface with a white abrasive pad to smooth away any small dust nibs. Then wipe on a coat of paste wax. If you wish to darken the appearance, you can use a colored wax. Wait for 30 minutes, then buff the surface with a piece of soft cotton cloth.
6. Rub out the finish
Rub out the stool with 0000 steel wool and then apply a coat of wax with a cotton rag. Let it dry and then buff with a clean cotton cloth.