If you get the settings right (in the options, google, follow roads, avoid highways, Coursepoint mode: auto etc) and you click in the right place, you can save a tcx file with advanced warning (which you set at save time) which you can upload to your Garmin Edge 500 and it'll warn you when to turn and which way to turn too.
If doesn't fit in perfectly with the previous flow, but, if you do have a gpx route you can TRY to create a tcx with warnings, this is how
- Create a gpx file using the various previously discussed methods
- Upload the gpx file
- Select the correct options as above
- Select Drag Edit mode
- Hold down control and click on the route
This gives some black dots. If you drag the route a little between the black dots it should add coursepoints. Beware though that the route may go a bit wonky depending on how google thinks your routing should be.
Now save the file. Set your CoursePoint warning distance and average speed.
Note: you can also add static coursepoints by selecting "Add POI/Coursepoint" and selecting "general" and then making a note. Found this really quite useful for the Great Windmill Caper