I'm not sure exactly what you are looking to do, but the welcome tool is the only automated tool I know of that can send messages to a user's message wall on your behalf. It is a single, pre-determined message you must decide on beforehand that will be sent to all new users when they make their first edit.
Templates on the other hand, can be used to format, display data, or lift data from other pages to display on the current page. However, they don't edit other pages directly. Using a template in conjunction with a message wall would still require the user to directly visit the other user's message wall to leave the message manually. - Sitb(Message wall / Talk page) 09:52, July 30, 2019 (UTC)