Display settings meta box under each course from which you can configure the time and weekday that lessons will be dripped on.
The dripping period will be fixed always (one week).
Select the day you want to make the lessons available at.
Set the exact time you want the lessons to be dripped on, on the specific selected day.
The time format is 24 hours
Set the time to make lessons appears if user enrolled before this hour of the chosen day
Example: If they sign up for the course on a Wednesday before 4 pm, they should have access to their first lesson at 6 pm. If they sign up for the course on a Wednesday after 4 pm, they should gain access to their first lesson the following Wednesday.
Enable/Disable sending emails to users when a lesson is available
Save all data.
WP Cron job will be running to drip each lesson to all users on the configured weekday and time. and send emails on lesson day, that lesson is available.