https://www.ycombinator.com/library/6t-how-to-apply-and-succ...

There's also a separate short talk on creating luck that has an interesting story about how Brex started, and also about how sometimes you need an "outsider's philosophy":

https://www.youtube.com/watch?v=NmEyx9TEkRw

These helped my thinking. The application is a helpful way to think about your startup even if you don't submit it. And once it's done, you might as well submit anyway :)

Good luck!