There isn’t really a good method. 
But, yeah. That’s still the idea. I don’t think anything has changed in Discourse since then. Typically, I’d do a couple by hand to make sure that it does what’s expected. Also, make a backup first, and maybe put the site in read-only mode so that if you do need to restore the backup you won’t have to throw away any posts made while you were mucking with things.
Without knowing a good bit more than is easy to communicate in a forum I can’t tell if that’s really the best way or if there’s something simpler. You might be able to just gsub the paths of the URLs, for example. If you’ve got a budget you can contact me or ask in Marketplace .