LOL, completely valid method. But that quit working on the interstate in Kansas City about 5 years ago. Everyone seems to drive so damn angry or with their head up their ass while they are texting, eating, putting on make-up, or reading a book...
When I'm driving in town or on calmer roads I still employ this method, but on the interstate they always seem to take it as a personal offense. The triple flash is reserved on these roads for quick stops, hoping the person behind can look up from their book long enough not to kill you.