Favorite→RT
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Favorite→RT is a tool that allows you to setup another Twitter account and have it automatically ReTweet the favorites from your primary account.
It will check your primary account for new favorites every 5 minutes, and then RT them.
Create a new account on Twitter to be used to RT your favs
Tip: if you use Gmail, you can add + something to your username to get a "new" email to use with twitter. (ie user+blah@gmail.com is the same as user@gmail.com)
Click the "Sign in with Twitter" button bellow and pair with your new favorites account that you've setup (this account will be doing the RT'ing).
Once you've logged in, type in your primary account that you use to favorite things with
Don't forget to click save when your done. If you want to stop using this service, leave the box blank.