Go ahead, plan your route on your computer using Google. Drag the marked line to the roads and interstates you desire.
In our sample route from Nova Scotia to Panama City Beach, we wanted to go via I-84, not I-95 where the normal programming will take you.
Once you get everything set up the way you want on the computer, pick a point on I-84 in the direction you want to go.
Zoom in real close at some point, zoom in close enough that you can see both lanes of the interstate.
Make sure to keep the mouse pointer right on the middle of the interstate in the direction you are traveling.
Right click and select DropLatLng Marker. (red arrow above)
A marker will appear with the coordinates listed.
(Later when you zoom out again, the marker numbers will be in a small box near the interstate or roadway where you marked it. It may look like it is not on the exact highway point where you want to go, but it is.)
Program the Vehicle GPS using coordinates
Mark down the coordinates you were given on the Google map.
Now go to your vehicle and input the information. Depending on your GPS you may have to use the Trip or Waypoint feature.
1) First your departure point.
2) For the next destination input the coordinates from the Google map.
When you are driving on a trip programmed in this manner, voice directions and all work as normal. When you reach one of these coordinates it will say, "you have reached your destination." Then it will carry on with the rest of the trip, to the next coordinate you entered, or to your destination.
This method won't lead you into any strange towns you don't want to be in. In our sample case, we only use the coordinates once. You could use them several times depending on any variations you desire during your travels.
It is even practical to make your own printed map booklet if you tend to repeat a trip yearly or more often, with these coordinates saved on it. You can have variations marked as well, and you have a printed backup that will work on most GPS brands should you lose the programming or change vehicles.