Guide Their Eyes
Video is a one-way form of communication, so user's don't have the chance to ask you to clarify or ask "Where does X fit in?" This places the burden on you to guide their eyes as you explain how all the little pieces of the code fit together. When your application has a "flow", "X triggers Y, Y triggers Z", make sure to "show the flow" by walking them through where each chunk of code fits. This involves a lot of mouse movement (or fancy keyboard selection shortcuts) and hightlighting to bring it all together.