All good ones. Another cool one is to number the stop signs sequentially. While you may not know which direction is fastest to the trail head, you know if you are making progress. Yager has done that on a few of his trails.
As for adding those numbers to the maps, very very easy IF I have waypoints. A guy just needs to ride the trail & set a waypoint for each item, naming the waypoint for the appropriate #. Easy to take that and put it on the maps.
GPS is a better way, no question then. We've done some of the road names on signs in Geels. Some at Gladwin too, but those signs only last for a month or so and then they get ripped off.