How do I regenerate posts during testing?

I'm still tweaking my first few feeds (ex. editing the section that is appended to each post) and I'd like to regenerate posts that have already been processed (before my feed changes). How do I do that?

I am specifically asking because I am testing one feed, and some of my edits are showing up immediately on the existing draft post, while some are not.

ex 1: I started with a shortcode in the "append" section, and when I saw that was not processed and just showed as text, I removed it... on the preview post, this change shows up

ex 2: I changed the feed title, but the %FEEDTITLE% in the append section is showing the previous feed title, and not the new one

ex 3: I removed the value for "Link to original source" (because it is all now in the append section) but the previous value is still showing up in the preview post view

Can someone guide me to flushing out the processed data so I can process anew? I don't want to lose all my feed settings so I don't want to just nuke the autoblog table.