Hi,
Normally the person who restrings your pearls washes them first and usually oils them afterwards. If you are restringing your own pearls, you will also be the one who decides if and how to wash and oil them. If the pearls are not very dirty, take some castile (also spelled castille) soap foam it up in your hands, then gently rub the pearls in your soapy hands and rinse thoroughly and then let your pearls soak for a bit in a jar or bowl of chlorine-free water before toweling them dry and restringing. Oiling is optional. Good pearls do not need oiling. If you feel the need to oil the pearls after drying, use a colorless mineral oil or cotton seed oil. If the pearls are very dirty wash them in a salt slurry and then rinse 5 times in chlorine-free water.
Zeide