Hey thanks for the suggestion. I actually use this strategy already, but the issue is that this only tells you what the general stuff most people will learn is. As far as I know this doesn't help with finding what the current problems are in the field.

However, I think that professors generally are very willing to help people who are interested, even if you aren't a student. Actually as far as I can tell usually they don't even ask if you are a student.

In addition to that you also can typically know how an undergraduate would progress in the courses from the universities as well, through stuff like graduation plans etc.