If a powerful rifle is to be mastered, the shooter must be dedicated and single minded to that end. The first step is to ensure the rifle fits properly, and that the scope is mounted far enough forward that it won't tag you. Glass bedding reduces but does not completely eliminate the potential for split stocks. Most flinching is a result of severe muzzle blast, so wear hearing protection. The discomfort associated with recoil is largely subjective. Shooter A is able to tolerate more recoil than shooter B, but he might loose this advantage if he is given a rifle that produces the same muzzle energy, but does it through increased velocity rather than increased bullet weight, because the recoil impulse occurs over a shorter period of time, the recoil will feel much worse; hence the claim that big bores push rather than kick. While this might be true, there are some big bore rifles that push enthusiastically.
A weight lifter over time increases the amount of weight on his bar, the shooter does likewise. He starts with a moderate load, then increase the powder charge as his comfort level allows. Do not shoot more rounds than your comfort level allows, if you can shoot 5 that's great, but if you can't manage 3, the load is too much for you, and you ought to back off another grain. Don't let that rifle hurt you. When you can manage 5 rounds, without loosing your concentration, add another grain of powder and drop back the number of rounds you fire. When shooting, concentrate on the mechanics of the shot. Start by finding then checking your natural point of aim, your position, your grip on the rifle, the position of the stock in your shoulder, breathing, relax, sight picture and aiming, pressure on the trigger, and follow through. Concentrate on each step. If you find your mind wandering, stop and take a break. The lower and more stable your position, the more uncomfortable recoil will seem, whereas offhand seems quite tolerable.