Ask HN: Do you have a process or a framework to learn specific skills quickly?

Any suggestions/ frameworks on how to learn specific skill, retain the knowledge and be able to share it(in for ex. written form)

I usually jump in straight away and start learning "on the job" but I realised that I forget too much and i do not have any notes to refer to later on.

Examples of specific skill: - How to write a good cold email - how to learn some snowboarding trick - how to store your bitcoin safely etc.