Sand the wooden banister by hand using progressively finer grit sandpaper to get a smooth finish. Start with 80-grit sandpaper to move any residue and leftover old finish.
Re-sand it with a finer sandpaper, such as 100-grit, and give it one more good sanding with 180-grit, superfine sandpaper.
Apply stain by dipping a sponge or rag into the stain and rubbing it on the banister until the entire piece of wood is wet with stain. Gently rub off excess with a soft rag. Allow it to dry for half an hour.
Polish with wood polish such as lemon oil to bring up a natural shine.
Make your own brass polish by mixing the juice of one lemon and baking soda or table salt. Squeeze the lemon into a small bowl and remove the seeds and any pulp. Add salt or baking soda to make a thick paste. If you have an exceptionally long banister, you may need to double the portions to get enough brass polish.
Apply the paste with a soft cloth to the brass banister. Work the paste into the brass going with the grain of the metal to remove patina and dirt from the banister.
Dip an old, soft toothbrush into the paste, and clean areas too small to reach with the cloth.
Rinse off the brass with a cloth dampened in warm water.
Reapply brass cleaner to any places you may have missed or that didn't come clean the first time. Rinse again when you're finished polishing.
Dry the brass quickly to avoid leaving any water spots.
Buff with a chamois or microfiber cloth to bring up a sparkling shine.
Lightly coat the banister with the thinnest layer of olive oil to protect the finish. Buff it in well so there is no residue remaining on the banister.