Redirect payment method documentation.

I don’t need to mention the lack of Magento documentation so here’s what I need to do and I am having trouble implementing it.

1. Register a payment configuration page in the Admin (Done)
2. Register a new payment method in the Front
3. User clicks Place Order, I make a request afterPlaceOrder and get a code from the external payment service to associate with current Magento order for later reference
4. Redirect user to external url
5. When payment succeeds/fails they are redirected to the callback URL (Done)
6. Create a callback url to handle order status logic (Done)

I am having massive issues finding how to register a simple payment method that only redirects and nothing else. Everything I’ve found so far, including the official code examples and the documentation are outdated (Doc 1) | (Doc 2)

How does one actually learn how to do stuff in Magento?