To re-oil wood furniture, do it in a shaded place or after the sun has set. Oil can dry quickly on the surface when exposed to heat. If you need to sand the furniture, use 150-grit sandpaper and sand in the direction of the grain. Apply the oil with a brush or cloth and let it sit for 15-20 minutes. After 15-20 minutes, wipe away any excess oil with a clean cloth. Let the furniture dry overnight or for at least 24 hours before using it. Re-oil the furniture once a month or when water droplets no longer bead up on the surface. You should also re-oil furniture that is kept indoors, but it is not necessary to do it as often.