I use the block rules as a fianl safe guard and as a default tool to debug mistakes. Even the applications have their allowed rules and then followed with a block rule.
With all software firewalls whether rules based or application based such as the ZA, the best method to debug mistakes is check the Logs. These will show the allowed and blocked events.
We all started without knowing about firewalls and networking. We all had to learn this somewhere at some time or another.
Actually I consider myself fairly knowledgeable, but I still keep learning new things or get more details.
I am glad I could help you