find a sling you like and use it
Making the rifle more compact and better balanced will go along way toward making it less of a burden to carry. Cut the barrel to 18", mount a lighter scope with light weight rings and mounts will help. you need a good sling.
My best suggestion is to find a tactical sling that you like. One that will allow you to rapidly shoulder your rifle. Getting the weight of the rifle off of your arms and onto your shoulders will make a big difference over the course of the day.
I often carry a nearly 14 pound 308 target rifle to hunt Antelope, I could not carry that beast all day with out a very good sling.
Superman, you are a mean drunk