To make anyone a better play, practice makes perfect. When players are introduced into certain drills, they get better at what they are practicing. If i become a coach, i would make the players run certain drills to get better.
One of the disadvantages of being a baseball coach, is your always on the road for games. Major league teams travel all the time, and are always away from their family. If i was to become a coach, i would fly my family around so we wouldn't be apart so much.