A great, general tool for baseball/softball and hitting is a heavy baseball. The standard baseball weighs 5 ounces. Hitting a ball that is heavier, by even a few ounces, is a large difference by percentage, and yields significant results. Imagine a 20% increase, to a 6 ounce baseball: become accustomed to hitting that, and the regulation ball feels light by comparison, and flies faster and farther when hit, all things being equal.
There are multiple commercial heavy baseball products. A remarkable product is the Total Control heavy ball, available in 2 sizes/weights, each in a distinctive canary yellow color. The smaller-diameter TCB Ball is the same approximate diameter as a regulation baseball, and weighs almost 3 times as much. The added weight requires the commitment and intent to drive through the baseball with a powerful follow-through. The Atomic Ball is larger in diameter, beyond the dimensions of a softball, and weighs 6 times as much as a conventional baseball. This mammoth ball requires a precise strike, or else the weight is displaced and the ball fails to fly.
The true selling-point of either Total Control heavy ball is the pliable nature/material. The ball compresses upon impact, and sinks into the bat much like a circular sandbag or beanbag. The rebound, or trampoline effect, is eliminated and the batter is forced to, in essence, 'catch' the ball on his bat and 'throw' the ball into the field. A long, continual swing into and all the way through the ball is required in order to hit the ball farther than several feet. Then, upon subsequent hitting of a regulation baseball or softball, the regulation ball feels like a lightweight tennis ball or Super Ball.
Use a Total Control ball and see/feel/learn the value of a strong, long follow-through. Get stronger, hit longer. Get Total Control, and be in total control.