This is the million dollar question I have too, but have yet to really sit down and experiment with it.
But to extract a personality, I am thinking of embeddings or fine-tunes.
For fine-tunes, see my babbling rant at Extracting Personalities from past Conversations?
For embeddings, I haven’t posted much about it, but I am thinking of the standard Q&A approach found here, and ask GPT-3 to summarize in some way that will preserve the tone. Where the data embedded is a bunch of things that person would say/think/believe.