Clean your leather sofa before moisturizing to provide a clean, primed surface that's ready for moisture. Mix 1 part distilled white vinegar with 2 parts food-grade linseed oil. Apply this mixture to the sofa with a lint-free cloth and let it soak in overnight. Buff into the sofa the following day to complete the cleaning.
Apply a simple moisturizer such as olive oil or linseed oil to the entire surface of the clean sofa. Rub in the oil with a clean, lint-free cloth.
Apply an extra coat of oil on dry spots, allowing the oil to soak in for several hours or overnight. Afterward, buff the oil into the surface of the sofa with a cloth.
Repeat step 3 until all spots appear sufficiently moisturized and the sofa has a rich, shiny finish.