In Twitter there is no option for sending direct messages (also called private tweets) to multiple users at a time. It is somewhat annoying and a time consuming process.
But it is possible now with a Twitter tool called MultiDM. With this tool you can send direct messages (DM) to 12 different users at a time.
It’s very simple to use. Just enter the TweetGuru MultiDM twitter app page and login with your Twitter account. Then you can send DM (or private tweets) multiple users.
Visit TweetGuru MultiDM page here. (Via) – Also see Twitter direct message bulk deleter