Wood banisters can be refinshed without taking them off. They are often polished smooth by palms and fingers of thousands of people, and there is no trace of the old finish left on the wood. You can make a banister look like new in one afternoon with sandpaper and aerosol lacquer. You can add stain to darken for a retro look or leave it natural for contemporary style.
Sand the banister by hand with 80-grit sandpaper to remove all the dents and old finish. Wrap the sandpaper around the banister if its round and scrub it back and forth with your hand as you move along the banister. If the banister is flat, attach the sandpaper to a hand block and scrub the handrail with the block until the banister shows all bare wood.
Re-sand the banister with 100-grit sandpaper and finish by sanding it one more time with 180-grit sandpaper.
Dip a sponge into your selected stain. Wipe the stain on the banister until it is completely wet with stain and then wipe it off with a soft cloth. Let the stain dry for 30 minutes.
Spray the banister with a light coat of lacquer. Hold the can at a 30 degree against the wall behind and above the rail to spray lacquer on the inside of the rail between the wall. Hold the can at a 30 degree angle shooting up from the bottom on the inside between the wall and the banister to get coverage from the bottom. Make one long spray down the top shooting straight down from 20 cm (8 inches). Wait 30 minutes for the lacquer to dry.
Wrap the banister with a piece of 180-grit sandpaper. Sand back and forth up and down the rail until the rail has a light white powder all over it. Don't wipe off the powder.
Spray the banister with another coat of lacquer to finish.
You don't need to stain your banister. Skip stain if you want it finished natural. You don't need to add more than two coats of lacquer to a banister, they get polished sufficiently by human hands and look great with only two coats.
Lay down plastic or newspaper under the banister to aid in clean up.