Re your first paragraph: What's funny is that I get almost the same effect by avoiding writing ideas down. I find letting an idea sit and stew in my head to be a good vetting process.

If I forget an idea, that's a feature of the system, not a bug. If an idea survives for a while and I find myself coming back to it often, then after a month of it being an idea I might act on it. At that point the idea is a lot less nebulous and I have a pretty clear idea of where to get started and an idea of where it's going to go in the future.