Fill a wide-mouthed jar 3/4 full with one or more of the salts. Add one of the oils until the salt is just covered. Add the oils and mix well. Scrub your feet, especially the rough or calloused areas, well. Leave the salt mixture on your feet and wrap with a warm damp towel. Wrap again with a dry towel over top of this. Keep this on for about 5 minutes, unwrap and gently wipe off the salts and rub in any excess oil into your skin.