Ask HN: Any Financial Model Tips/Tricks?

Hey there, this is such a common problem I have to assume there are some good "new school" startup style SaaS companies that are good at financial modeling and projection, for managerial accounting. I'm a startup founder and I want to model projected/actual P&L statement, statement of cashflows, and so on. I use Quickbooks Online, and I have a bookkeeper and accountant, but am wondering what other software type tools people are using these days to get more sophisticated understanding of their numbers. Would also be interested in any great books, blog posts, or anything else other people in the same position have found helpful.