Ask HN: How do you work through large ideas?

I seem to constantly have 1-2 large ideas in my mind that I chew on in the background, which seem to arise (or give way to something bigger) from reading or a lengthy discussion with a coworker or friend. For example: "what is the best way to organize a liberal democracy of >100M citizens?"

I'm wondering if there is an approach people have that best helps to organize, prune, and work through large, fundamental ideas such as these that they'd be willing to share.