We found that this double step (enrol to the course+session) was complicating things for end-users.

We ended up setting up Seminar direct enrolment+Guest enrolment within each course. This way, a user can take a look at the course content (there's some information about the course/prerequisites etc). Then, if they register for a seminar, they are enrolled in the course.

You could even have just Seminar direct enrolment without guest access - then, if a user looks at the course summary in course catalogue, they see the list of events available for enrolment.