> It's like trying to show how to do OOP in C.

Actually, I'd think that would be a super valuable to a C developer. Learning to implement OOP patterns in C would provide practical patterns that can help architect C software. For non-C developers, it'd also provide fundamentals of how OOP actually works. C developers have been implementing OOP patterns since well before C++ existed.

There's lots of resources, and practical examples of this. GObject provides an object system used by both Gnome and GTK. Check out "Object-Oriented Programming With ANSI-C" for a book on the subject.