Every cast iron tutorial on the internet makes the same mistake: too much oil. A thick coat will gum up, stay sticky and smoke like a chimney. You want a coat so thin it looks dry.
Preheat your oven to 500 F. Rub a teaspoon of flaxseed oil or grapeseed oil into the clean, dry pan. Wipe it off aggressively with a paper towel. Yes, wipe it off. The film that remains is what you are baking on.
Place the pan upside down in the oven with foil on the rack below to catch drips. Bake for an hour. Let it cool in the oven. Repeat this three or four times for a new pan.
After that, the best seasoning happens through cooking. Eggs, bacon, steaks, cornbread. Every meal adds another microscopic layer. In a decade your pan will be glassy black and non-stick without any help.