Put dropcloths over a floor in a well-ventilated area such as a garage or shed.
Squeeze degreasing dish soap in a plastic bucket and fill with warm water. Thoroughly clean the barstools with a sponge and the degreasing dish soap. Rinse with plain water and a clean sponge, then allow to air dry.
Put rubber gloves on your hands and dip a rag in mineral spirits. Wipe down each barstool with the rag to remove the old finish. Let the mineral spirits evaporate off the barstools, then wipe down with clean, damp rags. Let the barstools air dry.
Sand each bar stool with medium-grit sandpaper to remove the old finish and roughen the wood, going in the direction of the wood grain.
Paint a coat of gel stain on each barstool. Allow the stain to seep into the wood on each barstool for about 10 minutes. Wipe off the excess gel stain with clean rags.
Use a steel wool pad to apply a coat of wood varnish, brushing on the varnish gently in the same direction of the wood grain. The steel wool will help the wood varnish to penetrate the grain and blend into the wood.
Allow each stool to dry for three to four hours before using.