All surfaces to be oiled or painted should first be cleaned with a paint cleaner. If the surfaces are affected by fungus, they are cleaned with a special mould detergent. Rinse thoroughly with water.
Old, flaky paint is scraped off. In corners and angles you can use a small triangular scraper, in larger areas a larger paint scraper. Then sand the surfaces with an abrasive paper to remove any fibre residue and unevenness.