I authored a two-page instruction guide explaining the magic numbers approach. I tried my hardest to make it as readable / accessible as possible, it can be downloaded by clicking this link.
The magic number video and cheat sheat document describes the potential for recording passwords by using a word processor or spreadsheet. Clicking on the aforementioned links enables you to download blank "password register documents."
Improved (Simpler) Video Explanation for Headway
I realised that while my explanation was conceptually accurate, it didn't describe matters as simply or as clearly as I'd intended. I made an extra video, which was the basis a series of Zoom chats with the Headway charity organsiastion - see link.
The video below is my attempt at giving pragmatic advice around password management. It's aimed primarily at the elderly and unskilled, utilising an approach which I've called "magic numbers". The video can be viewed on YouTube directly via this link.