As I have stated a couple of times already, the brush engines are very deep. This is the longest chapter in this book and I could have easily made it twice as long! Hopefully what I have provided has given you a good grounding on how the brush editor is organized and functions. From here, you should be able to experiment and modify brushes to your liking.
The documentation that Krita provides on the brush engines is good
(https://userbase.kde.org/krita/manual). Sections like the bristle engine (previously called hairy engine) are a little sparse so you might have to do a bit of digging to understand the settings. Even though I have spent time studying this, I still consider myself a novice. There are a lot of creative brushes that have yet to be discovered. If you create some interesting brushes, share it online!
Artwork by Sylvia Ritter