It can be difficult, I know that it can sometimes be quite a task to get clients to understand it all. It would be better if the WP auto draft feature included custom fields, but I doubt that will happen. One of the major issues is that if the post title, post content or excerpt for the post have not been edited, the auto save doesn’t even fire to begin with. There is a solution to save that ACF fields during the auto save, but it depends on the auto save actually happening and that’s where it falls apart since the WP JS only looks for updates to built in fields. https://github.com/elliotcondon/acf/issues/585
