I would say general knowledge in many domains may help with this as you can try and approximate to the nearest thing you know from that domain.

How you get good at being a generalist is the tricky part, my best bet is reading and doing a lot of trivia (I found crosswords to be somewhat effective at this, but far from being efficient)

No, that has nothing to do with it. Trivia helps you narrow down an interval. It is not necessary to construct a correct interval, which can be of any width.

I am dying inside imagining someone who had to use crossword puzzles to learn how to read. There must be a better way to educate the masses!