When I'm not gardening, I work in the Department of Horticulture at Cornell University. One of our professors, Ken Mudge, teaches an online grafting course that's also very hands-on. He sends plant material (hibiscus) and supplies that you actually use for the 'lab' part of the course.
He also teaches the principles so that you can apply what you learn to other species and situations. Like if you want to graft different varieties onto your fruit trees or onto different rootstock (dwarfing, hardier, disease-resistant etc.).