Anyone used Mail_Queue?

Does anyone have any experience using the Mail_Queue package? It's description suggests its suitable for my needs, but the documentation is spare, and I'm struggling. I simply want to add emails to a queue (in my case a MySQL table, 'mail_queue', the SQL insert for which comes with the package docs), and have them send according to the "time_to_send" field, then have them delete once sent. The SendMailsinQueue() function seems to send the whole queue, disregarding the time_to_send field. Am I supposed to set up a cron to invoke SendMailsinQueue? If so, what should the crontab settings be? The put() function loads two copies of each email into the queue, but if I set $delete_after_send to true, only one copy is deleted. Maybe I'm misunderstanding the purpose of Mail_Queue, or I'm expecting it to do more than it does. Can anyone give me a step-by-step example of how they implemented and used this package?