This really isn't as tough as it seems. I think it's a matter of getting comfortable with a batter, and setting the game up for success.
The first thing you should do, from the main menu, is head to settings and adjust the sliders. Improve human contact, power, etc... The things that make it easier to hit home runs -- Once that's saved, head down to home run derby.
Ball park is entirely up to you, but I've see encouragements on US Cellular Field (and you can grab the "Deep Dish" Trophy while you're there -- I did it at the LA Dodgers stadium so I could get the "Loud and Clear" trophy.
Batter is personal preference, but I did most of the home run trophy work with Bautista from Toronto. Add him to the list four times so once you're in the event, you can keep trying until you get comfortable with him rather than going back to the event over and over.
There's not real trick to the process, just takes a bit of time. After having switched the sliders to the improved contact, I was able to get the ten straight trophy with my first batter. Managed 25 HRs and got the trophy with ease! Surely it won't take long for you as well! Good luck!