At shorter to moderate ranges, there is a fair amount of leeway for angle compensation, as in you're only talking a difference of an inch to 1.5 inches at moderate angles. When you start looking at longer shots, it becomes more critical. And, if you're hunting steep country, you can expect to take steep shots: 25 degrees isn't uncommon in steep country and you could definitely get presented with steeper shots.
1. You can invest in a geoballastics rangefinder that will provide the scope compensation/turret adjustments for your specific set up. Some of the non GB rangefinders offer a limited amount of data, but if its not precise to your caliber and load, it may not be sufficiently accurate. I have an older Bushnell that does this but the closest setting for my rifle is not close enough to be accurate.
2. You can make a secondary DOPE chart with angle compensation factors. This could get complicated in sudden and stressful shots.
3. You can memorize a formula for your caliber and load
4. You can use an app (hardly efficient for real world hunting)
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Ultimately, you need to practice steep angle shots. The setup for such shots can be (and usually is) extremely frustrating and flustering -lots of adjustments, trying to get your pack in your lap to stablize the rear of the gun, bino harness in your way, your butt sliding down the hill as your're trying to get stable ..... all kinds of things going on.