News Flash: I didn't learn everything I needed to know in grade school, high school, or college. Neither have I achieved my early intentions of becoming a polymath by reading all the Great Books of the Western world and the Encyclopedia Britannica.
Thus it is no surprise that as I teach a broad category of subjects, I often find myself lacking the knowledge of details which I would like to share on various subjects with my students.
One pleasant way I have found to fill in the gaps is the wide variety of subjects offered by The Great Courses. At first, I bought their DVDs which are often on sale -- or found them at Half Price books or on eBay. But then I discovered that as an Amazon Prime member I could have access to a growing number of these videos online for a $10 per month subscription - and I don't have to add more shelves in the TV room. Amazon even offers a free 7-day trial of the collection.
I also have tried the writing course on MasterClass.Com in order to gain some perspective apart from just trying to gather lesson plans and methodologies. If the classical Lutheran education thing doesn't work out for me, I may consider taking the Steven Martin course on stand-up comedy.