Keep the velocities at gentlemanly levels, and start shooting it. It will turn you black and blue once, or maybe twice, and then you know the rifle. You don't perceive that you are doing anything different, but you just don't get beat up by it anymore. The closest thing I can relate it to, is riding a four wheeler over rough terrain. The first couple times you do it, you hurt for days afterwards, but then, you get the hang of it and you learn to move with the machine and it doesn't hurt you anymore. In fact, you learn to appreciate being able to feel the ground under the four wheeler. It's the same with steel butt plate rifles.
Just a few days ago, I ran about 70 rounds through my 1886 with a steel but plate. The load was RD 350 over 30 grains of 4227 and a Dacron filler (1650FPS). There was a time when that would have been really painful, but I didn't have so much as a red shoulder when I was finished.