I have a Garmin 1450LMT and use routes on it. I use Garmin's Mapsource to create my routes. After downloading from Mapsource to the unit I check the route. Sometimes the unit wants to make a change. I find out where the change occurs and go back to the Mapsource map and add a few additional waypoints then I reload the Mapsource info to the unit.
When we went to NY last May, I created our route in segments in Mapsource. I labeled each route the day of travel. In each route I had the fuel stop I wanted to go to followed by the campground we were going to stop at.
Every evening after we stopped I would load the next days route. It made the trip very simple.