For old and worn surfaces, i.e. doors and window frames that are very dark or uneven in color, or that have not been oiled for a very long time, we recommend the following treatment.
Follow these four steps:
Lightly sand with sandpaper
Brush off loose particles
Clean with a suitable agent to prevent buildup and discolorations
When the surface is clean and dry, apply a suitable oil treatment. Use a brush or sponge to apply the oil. Remove excess oil with a lint-free cloth to avoid shiny spots. For dry sanding on degraded surfaces, use 150 to 220-grit sandpaper.
Always remember to sand along the grain of the wood and not against it, to avoid visible scratches.