How do I use attack captions to make dialogue in battles?
This is very simple. All you have to do, is make an attack that doesn't do any damage. Then, set it to "show caption" and type in the section what you want the attack to say.
Make sure in the caption box you type "Dude: Blah blah blah" so that people know who is talking.
You may also want to make it chain to another attack which is also dialogue, so it seems as if they are talking back and forth. And you could add appearance to the attacks so that maybe a speech bubble appears when they say it, or the person wiggles.
One last thing, if you want it to only happen once, you may want the enemy to activate it, and make it so that none of the enemy's other attacks require MP, and the dialogue attack uses all the MP of the enemy. An common alternative trick is to add an invisible untargetable enemy to the battle which uses a slow chain of attacks to show a sequence of dialogue and actions.