Michael and I were rural fire tho that did involve some township work. We never relied on letterboxes. Just on a street (or rapid) number. So a simple number at the entrance would do.
If it isn’t already listed as a requirement or been arranged the dunedin brigade might like to do a practice on site. Practices can be quite boring so we used to take any chance we could of mixing things up and gives the brigade time to work out where things are at a new location. While there is no urgency. And we always liked the chance to have a good nosy too!! rgds roz