The gun's weight and bulk is a greater factor at the end of the day than in the morning. You are tired and less aware of what is going on around you, so you are certainly more likely to find yourself in a difficult bear situation than at other times of the day. If you are like me, for what ever reason I end up leaving with the sun in my eyes in the morning and returning with the sun in my eyes in the evening. This helps to ensure that if you do have a bear encounter it will be close, particularly if the bear is as oblivious to what is around him as you are, or I am.
Lots of folks who have never been close to a bear seem to develop some pretty strange ideas of what they need to do to defend themselves should a dangerous bear situation develop. One of these ideas is the tactical reload. While reloading under stress is a good drill to practice, I doubt it has much application in real life unless you carry a single shot for bear defense. I did for quite a few years, and I got pretty handy at reloading those things, but folks who choose the shotgun for self defense will find that the repeating shotgun with a magazine capacity of 4-6 rounds is a better idea. I consider it a mistake to have fewer than 5 available rounds in the gun, but more than 6 makes the gun unwieldily. Chances are if you are going to be able to solve the problem you will have to do it with 1 or 2 rounds, that is all there is time for, so tactical reloading while an interesting technique to master, doesn't really have an application in the bear defense scenario. This being the case, while we want the gun to be as light and portable as possible, choosing a barrel length that requires a shorter than standard magazine length is not a wise tradeoff in case you do need more than two rounds. You might have a failure to fire, you might miss with your first shot, and cycling the action is faster and simpler than the tactical reload.
Cycling the action brings us to the point of which action to choose. Most folks, myself included choose the pump shotgun. The pump shotgun has much going for it; low cost, good reliability under field conditions, etc, etc. But the pump does have limitations, and the person who chooses the pump must know those limitations. The first is the dreaded short stroke. This is where the shooter who is under stress, doesn't bring the fore-end completely to the rear of its travel before pushing it forward again. Invariably this results in a gun that will not fire. The auto-loader never short cycles. Provided a quality auto-loader is maintained to the same extent as a similar quality pump, reliability will be the same. The fixed fore-end of the auto provides a more stable shooting platform, than the wobbly fore-end of the pump. Finally, if the shooter is injured and only has one arm with which to operate the gun, it is easier to fire multiple rounds from the auto with just one arm working than it is from the pump.
Most shotguns are intended to be used for pass shooting at waterfowl. The use of the shotgun for self defense is a departure from this more traditional roll, and the handling of the gun takes on a more rifle like style. As a result most adults will find the LOP of an off the shelf shotgun too long. The recoil pad should also be upgraded in many cases as well, and the LOP for most folks is best somewhere between 13"-13.5", particularly with bulky outdoor clothing. Shortening up the LOP and using proper shooting techniques will reduce the felt recoil of full powered slug loads, bear defense is no place for reduced recoil ammunition.
Finally we come to the crux of the OP's problem, how to carry this thing. First of all, when going through heavy cover where the visibility is marginal, the gun should be in your hands. Your firing hand should protect the trigger, preventing branches from entering the trigger guard. Once you are clear of the heavy cover, the gun can be slung. For the last 10 years I have used a simple 1.25" nylon carry sling, but I am now going to try an upgrade. I'm not sure how well this will work out, but various military and police units have had success with it, so I though it was time to try it myself. This is what is often referred to as a team sling, a 3 point sling, or an H&K sling and is attached to the weapon by two sling plates, one at the juncture of the stock and the receiver and one behind the mag tube cap. The advantage is that the gun is carried in a firing position in front of you, or can be pushed out of the way behind your hip when you are engaged in a non-shooting activity. Thus, the shotgun becomes more like the handgun in that it is worn rather than something you have to go and get when its needed. How well this system will work out, I'll let you know after I've used it for a while.
