It might be useful if you say what you're trying to become an expert in. Ask a vague question, get a vague answer.

> always come out frustrated

You can't stop there.

Yes, a lot of expert knowledge is locked up in the heads of experts. It is very hard (if not impossible) to write down all the implicit and explicit knowledge that experts have, so it doesn't always happen. It's very hard to become an expert alone. I think this also says something about the nature of expertise: it is something that is constructed by experts themselves in their minds. There was a story that a famous mathematician would tell is grad students, holding up an important book, "You should know everything in this book ... but don't read it!"