I had tried to follow the solutions below, but I still encountered that it was somewhat difficult to finish off the achievement. After getting frustrated so many different times, I found the easiest way to do this.
Follow the first steps from the below solutions (x DRabNORMal x), then when you are done editing all the rosters/sliders for both teams you wish to choose, enable the "Super Bunt" cheat in your Cheats Menu. You can also enable any other cheats that you think that might make it easier for you ( Cheats still allow the achievements to be unlocked ).
When you enable the "Super Bunt" cheat it will allow you not having to time your swing, and allow you to just hold the Y Button (Bunt - Classic Control) shortly after the pitch. Following these steps you should hit a homerun every single time.
Around the 4th inning I got the achievement, for some of you it might pop earlier or later.
In my opnion, the cheat takes away from the frustration, and makes it easier for people who aren't as good with timing their swing to finish the achievements in no time.
Using this set up you will also be able to finish all the achievements in the same session.
Hope this helps. If anything is unclear, don't hesitate to ask.
Saving the game after each homerun will cancel the achievement. You have to try to knock out the achievement in one sitting, which shouldn't take more then 30 min. once the sliders have been adjusted and the cheats have been enabled.
Also thanks to Kulkan:
"Been looking through guides and it takes more than just bunting the ball. If you hold bunt too early, it causes grounders or fly balls. The trick is to wait until the ball is in the air, coming at you, before you hit Y. I was struggling for hours with this, tinkering with settings and all that and reading guides. It wasn't until I started waiting til the last second to bunt that I started getting homers like crazy."