What is the best way to give non-guild members read and write access to the public section of your forum?

I would like that non-guild members can leave forum posts on the public section of our forum, but in order to do that they need to register. How do you solve this problem in the best way?

I was thinking about setting "Settings - User Registration" to "Allow anyone to register on website". and set viewing access for the public forum to "Acess: All" and posting access to "Access: Registered Users"

This would allow all new users to post on the public forum. However I guess that now i need to use a registration form for users to apply for the guild, and if approved add a tag automatically (lets call the tag members), and set viewing and posting access for the non public sections of the forum to Tag: Members only.

This would separate the public and the non-public sections of the forum. Is there a better way of doing this?
Any suggestions would be much appreciated!