I have used peanut oil on copper the way you describe olive oil on
steel. And you’re right, it is harder than it looks! With the
peanut oil, you have to heat it carefully with the torch and not let
it smoke. When heated slowly, the patina turns a deep, warm brown.
When overheated, it turns a crispy black! You can also tell by the
smell if you’re overheating it, especially if you frequent diners.
Thanks for telling us about the olive oil on steel!