An Amish cast iron skillet is an heirloom. It might be 100 years old — and works better than new.
Seasoning
Apply a thin layer of flaxseed or canola oil. Flip upside down, bake at 230°C for 1 hour. Repeat 3–4 times. Oil polymerizes — creates a natural non-stick coating. The more you cook, the better it gets.
Washing
Hot water with a stiff brush. No soap (soap strips the oil coating). Coarse salt as abrasive for stuck food. Rinse, dry completely, lightly oil.
Don'ts
Don't soak — it rusts. Don't dishwasher — kills seasoning. Don't cook acidic foods (tomatoes, vinegar) on new pans — acid eats young seasoning.
Restoration
A rusty skillet isn't trash. Soak in 1:1 vinegar-water for 1–2 hours. Steel brush off rust. Rinse, dry, re-season. Good as new.