I found a new product a few years ago that really helps in the field dressing of deer & bear. The product's name is Butt-Out and for those who chuckle at it's name or it's uses you might want to take another look. I've used it on several deer the last 2-3 years and it has never failed to save me time and mess. I've had a couple of skeptical friends chuckle when I pulled it out of my pack (weighs about 2 ounces) and got ready to utilize it.
I then look them in the eye and simply say, "watch this and then comment to me". When Ed has the anus cored out and tied off in a total of 1 minute and also done clean as a whistle, to the hunter they simply sat and stared for a few moments. I'm pretty sure each of them owns their own B/Os now, And yes, we tried it, with great success on a Maine black bear last year. The guide was very skeptical and simply stood there shaking his head in disbelief at how well it worked.
Try it, you'll like it!!