Hey Chris, PM me if you have any questions about GAIA GPS. I'd be happy to share what I know about it. Also, don't be afraid to push buttons and see what it can do for you. You can't break it!
As for downloading layers (maps), I download whole mountain ranges at a time when I;m connected to wireless. You could, in theory, download a whole state in a relatively short amount of time and that would always be on your phone. You could also drop a pin (waypoint) in the middle of the wilderness (or cornfield for that matter) where your kill is as you pack loads out. You could then navigate back to that kill, using your phone, in the dark to carry your last load out. It works just like a GPS because it is a GPS, on your phone.
Not all map apps are equal though. You get what you pay for. Free map app? Probably not so good at finding your kill in the dark.