This idea works well if you are struggling to make dialogue unpredictable or are having a hard time distinguishing between two characters’ voices.
Get with another writer friend, preferably someone who is familiar with your story or style of writing. Brainstorm the general plot of the scene you’re about to write or rewrite. Don’t get into too many details but both of you should know where it begins, where it ends, and what vital information or action needs to be revealed or happen. Then choose who will write from which character’s POV. Take some time to get into your character and remember that you can only write from inside that character’s POV.
Take turns writing out the dialogue and action. The beauty of this exercise is that you won’t exactly know how the other person is going to express their character or even exactly what the other person is thinking or going to say. It’s like a real conversation, unpredictable.
In the end read back through the scene together and maybe iron out a few details for clarity. Discuss the vision of both characters in hindsight and make adjustments accordingly. You won’t necessarily have to keep this draft of the conversation but it might give you that push you needed in order to make the scene work.