Sending reminders to complete learning item

Content

Hello,

We're looking for a way to issue reminders for employees 1 week before their required learning assignment due date. I've tested this with myself as a learner using the Mass Action button and received 8 nonsense emails in the space of an hour.. I know I need to set up a template if I'm wanting to use this option but I'm interested to see if others have used this and how it's worked? 

I also tried using Send Email which is far clearer and easy to customise but it looks like I need to manually select those I want to send the email to which isn't practical with 3000 people.