Safari Sling
You must at least look at a Safari Sling. If do much walking these things can't be beat.
You can sling your rifle at the waist or on the front or back shoulder. The gun can be brought up for a quick shot with minimal movement and you can rest your arms on the gun as you walk. Plus... they are inexpensive.
I've introduced these slings to many of my buds and all end up with one in a year or two. Available at Cabela's and many more places.