Yes, you can do this using the Share Article feature, see this page to add this to your Journal entries.
You can also add a Twitter button to each journal post. After generating code for this from Twitter, you can add this to your journal tags by following the steps on this page.
Alternately, you can use a third party service like Twitterfeed to automatically post to Twitter when you update your journal:
http://www.twitterfeed.com