This is what I did to share my posts on Google+ to Twitter and then Twitter to Facebook:
Google+ to Twitter:
- Go to http://manageflitter.com/plus and connect with your Twitter account, choose Basic Plan (free one)
- Go to http://manageflitter.com/plus again and enter your Google+ URL
- Start sharing posts from Google+ toPublic, they will appear on your Twitter feeds.
Twitter to Facebook: follow this guide.