Hi Christina

It is possible to send a message to Audiences through Site admin > Users > Accounts > Bulk user actions.

1. Choose the Filter Audience ID is equal to "AUD0001" or the Audience ID you want to send to
2. Add the users to the Selection
3. Select Send a message under 'With selected users'
4. Type in the message to be sent to these users

I can't think of a more automated method.

Regards