If the bunting method with 2 controllers isn't working so great for you, there's a much easier method.
Still use 2 controllers, and when you are batting have controller 2 intentional walk you over and over again. To do an intentional walk, as the pitcher hold RB until a prompt comes up. Then press A (yes).
This extremely simple method allows you to only press 2 buttons, and the player 1 controller doesn't have to be touched at all, unless it was to power off.
Each RBI should take about 10 seconds each, so at that pace you'd get 100 RBI's in under 20 minutes, and 1000 RBI's in about 3 hours
*Take note that this is very buggy, and more than likely your tracker will freeze. If this is the case, then keep going until is starts tracking again*