I retraced the track in MapSource. The short off road bits were made by going into the Edit tab and clicking: preferences>routing>direct routes
This essentially drops waypoints where you want them. I dropped those weigh points where Oklr had them. After I was back on a road I reversed the process and used "Auto Routes". When you hit one of the waypointed sections the screen will show each waypoint but it clearly shows the road or track in question.
As Oklr stated routes aren't for everyone but the venerable GPSmap 276 as well as the new Montana can handle a route like this.
I used the same method for laying out an 1100 mile route through Colorado, Utah and Wyoming last summer. It works fine.