Exclude category from all feeds but its own

I want to set up a category and have posts to that category show up only in the feed for that category, not in the main feed or any other feeds that happen to arise.

I’ve spent a lot of time Googling and tried 5 or 6 solutions, none of which have worked. I would like to be able to write here what I’ve tried, but I’d have to test them again to remember what went wrong with each solution. And each time I test this and it doesn’t work, a post goes out to my client’s feed that says “testing” and it’s unprofessional.

So, I have two questions:

1) Can anyone think of a way I can test this without broadcasting test posts?

2) Does anyone know the solution to the original problem – excluding a category from all feeds but its own?

I’d be very grateful for any advice.

Thanks,
Kim

P.S. I’m not currently using Feedburner for this site and am not super familiar with it, but will go there if that’s the solution.