At this time the only way to do this is to run dailymail manually from the "Dailymail" button on the main menu.
However, this is very likely undesirable as it will not only increment your test addresses 1 day but it will also increment users on your live lists with followups. The next release features an "Admin Preview" option as well as Quick Save/Load on every single message editing page so checking the format of your followups will be easier.
For now, your best bet would be to copy and paste your followups and send them to a test list.
