Just put the gpx on there and follow the line. If you come to a trail intersection, look at the garmin to see which way to turn. Look down once in a while to make sure you didn't miss a turn. This is literally how I learned all of the trails in North Jersey, and it's how I go on rides when I travel. Navigation assistance is unnecessary.
you are correct its unnecessary, but im spoiled and (if im in a group) lazy, its nice to not worry about missing a turn. still have to watch the map ect. just extra warning