I normally work on WordPress.org and WordPress.com - so this is coming from a Blogspot n00b. (I started this Blogspot account to experiment & learn). Pls help me along if I'm mistaken at any point.
• START •
Basically, just add /feed/posts/default or /feed/posts/default/?alt=rss after your Blogspot.com URL. They both work, so pick one.
2. Click on "test rss feed", it should give you a big green OK. You can tweak the settings etc, then Save Feed.

← If you see this, fret not, it'll still work. It just means it's not tracking any stats.
3. Go watch one episode of Dexter. Come back and Twitterfeed should have nicely fed your blog posts to Twitter.
• FIN •
• If you feel like you need to track clicks etc, in Blogger.com, go to Settings > Site Feed, click on FeedBurner
• So you Sign in with your Google account etc., and you do a quick-n-dirty because you just want to get it to work.
Not sure if this next step is necessary/ relevant, but back at the Blogger.com ranch, you paste your new http://feeds.feedburner.com/potatox feed URL in the Post Feed Redirect URL field, Save Settings, go back to Twitterfeed to see if it works now, and it spits out an awareness API error.
That's cuz you did a quick-n-dirty, you squirrel.
This is the part that (hopefully) gets it to work: go back to Feedburner.google.com, go to Publicize > Awareness API , click on Activate.
★★★ SUCCESS! ★★★
The feeds take a wee while to show up on your Twitter stream, so you must can has patience my fren.
I still think there has to be a better/ quicker/ less painful way to do this for Blogger?