Restoring Cast Iron ware from normal wear and tear or rust
First wash the iron skillet with steel wool and little soap with water. If the cast iron is rusted immerse it into a bath of vinegar and water with a 50% ratio for about an hour. Then take it out and put some sodium bicarbonate (baking soda) on the skillet and wash it with water to neutralize the acid, then pat dry and place it on heat to evaporate any remaining water and moisture.
Next season it with a little bit of oil, be it Olive or Violet Oil, flax seed oil; cover all surface area and place it in the oven at high temperature for an hour or so, above the smoke point of the oil used. In case of olive oil its around 180o C for extra virgin olive oil.