User draws a mental line from their fist to their target ahead of time, cold isn't a type of energy to pummel an opponent with. It's a lack of energy. Once user has a mental path mapped out for their attack, the spread of their aura will drain the heat from that object while they approach. By the time user hits their target, the first layers of ice crystals should be in place just in time for user to break them. Ki attacks don't affect people the way they do plants or rocks. Any time this technique is used on another person or animal, their own ki instinctively fights against it, off-setting user’s energy as best it can. This is why the bakusai tenketsu doesn't work on people or animals when it will split rocks, plastics, and even dead wood. Even the minute amount of life energy possessed by plants is enough to disrupt the precise chain reaction necessary for the technique to work. The Setsuben Chuu will rarely freeze a person's body completely to the point that it will shatter due to their aura. If you put a lot of power into it and use it against an untrained person, it can have that effect, but a trained warrior would hardly need such sophisticated techniques for such things. Against opponents of even mild skill, the attack merely forms a layer of ice over their skin, locking them within a frozen shell. A reasonably powerful opponent won't be trapped by it for more than a moment, but it will slow them down but good, even after they get free.