I use a VTAC Sling. Check out this video, and you will see what I mean, video:
VTAC Sling.
As you requested, I can carry my rifle vertically down in front of me (on my chest) or behind me (on my back). I have both hands free to do whatever, use binocs, climb a barbed fence/post, etc...
If its in front of me, I can quickly bring the rifle up and get my sights on that coyote. For a long distance shot, I can tighten the sling down to help with stability.
I absolutely can not stand normal rifle slings anymore now that I use a VTAC sling. With a normal rifle sling, I usually have the trigger guard jammed in my back, and most of those slings are not long enough when you carry gear or have heavy winter clothing on. And like you said, "struggling over my shoulder" - it sucks, cuz the sling and rifle usually slip off my shoulder (what a pain)
So since you have a rifle (instead of an AR), you'll probably have to rig it so that you can have VTAC attached to the side of your rifle.