[CGamesPlay]

The Feynman technique might be helpful to you [0]. When you read about it you'll hear it's about "how to learn", so you might disregard it, but by the result of applying the method is a written page that fully expresses the idea. I would start with that and don't worry about the document becoming too large, just continue as necessary. Finally, aggressively edit the document. If it's very long there may be some "prerequisite" post to write before your desired topic, but you can mostly just pull out the prerequisite content, and then re-edit the original one to account for that.

[0] There doesn't seem to be a single canonical document to read but there's thousands readily searchable.