The Montana 680 is a powerful machine, full of great technical features and probably one of the easiest and best Garmin navigation GPS devices I've used.
Over the years I've used the eTrex, Montana, Monterra,the 64, ZUMO and the 276CX. What it gives away in size of the smaller screen and some 'nice to have' features in comparison to the larger units like the Zumo, it makes up for in performance.
That's not to say the Zumo or other navigators are bad, you can't really go wrong with a Garmin, it just depends on the features you're looking for and how you intend to use it.
My only gripe, the world beating 276CX, it was nothing more than a brick when it came to land navigation, and thankfully Garmin swapped it out for me.
But this isn't a device review, so I'll get on with the quick tip to stop you squinting when following a track.
There's plenty of hacks and ways to get into the files on most devices, adjust, change or add files, but if you're not tech savy, maybe leave that alone for now.
On the Montana, a really simple way to increase the track size is just use the Where To feature. It won't actually navigate the track, it'll just increase it's thickness and make it easier to see, you still follow it like a normal track, although your colour choice will be defaulted to Magenta like a route. If you're showing multiple tracks at a time, only the one you select will increase so it won't hinder what you're doing. It's also a good idea to select different colours for almost every track you have on the screen at once, that'll keep you from coming to points that crossover each other leading to confusion of which way you're meant to be going.
And if you're following a pre-loaded track and not interested in any map detail cluttering the screen, reduce the detail or turn it off altogether giving a blank background and just the line to follow.
Following a track line for the first time can be confusing, but it's not the line that makes it tricky, it's all the intersections and side tracks creating clutter, if you don't need them, try switching between on for exploring and off for just following a pre-loaded track.
Hope this helps
See you out there soon.