I was trying to figure out the same thing. Here’s what I’ve got. Download the WP plugin Advanced Category Excluder here:
https://ace.dev.rain.hu/
Created a private category for all posts you don’t want in the RSS feed. For me, I created a category called “No Broadcast.” In ACE settings you can exclude that category from RSS posts. You’ll still need to mark the posts “private” if you don’t want them showing up on your main page, so I also use this for posts I don’t mind being on the main site, but don’t want sent out to every RSS subscriber.
