Meanwhile, turn-by turn on the eTrex means auto-routing. As I've said before, it's absolutely fine for finding an address amongst a twisty maze of one-way streets in a town centre, or for getting you to the nearest railway station when your bike ride goes wrong.
If you want to follow a pre-planned route on an eTrex, your options are pretty much:
1) Navigate a Track. It will appear as a blue line on the map, and you can follow it manually.
1b) Have a Track set to be displayed without navigating it. It will be whatever colour you like, and you can follow it manually. You miss out on some trip computer stats.
1c) Use proximity alarm Waypoints with descriptive names for turn instructions, in combination with a Track. Bullet-proof to follow, assuming you don't go off-route, but a *lot* of work to create and manage.
2) Navigate a Route in 'off-road' mode. As (1), but with tighter routepoint limits.
3) Navigate a Route in 'follow road' mode. The device will plot a route between each routepoint using the map, and give you turn-by-turn instructions. The problem is that if you want it to follow specific roads, you have to put work into positioning the routepoints to game the algorithm (typically, placing points in the middle of sections of road you want to use). This is subtle, and only about 95% reliable, due to differences in the algorithms used by Basecamp[1] and the device. There's also a limit of 50 routepoints for auto-routing, so you need a separate Route for every 100km or so.
My preferred approach is to combine (1b) with (3). That way I get prompts at junctions, but can see when it's trying to lead me astray.
[1] For this to stand a chance of working, you pretty much need to be using Bascamp and the exact same map as the device will be following.
