Anyone done it? What is the best way, time, etc? I think capturing and keeping my own strain of Brett would be super badass. I think I could get a microbiologist to help me out.
Yeah, that's what you will need (a microbiologist). They will probably put it on agar plate and grow it up and isolate it from there. I haven't done this in my homebrewing 'career' but did back in college and it is straightforward enough.
I know a microbiologist who cultured a strain of Brett A from a up from a bottle of french cider. He put it on agar an isolated it down to a single colony, then built it up from there. Now he keeps it in a wine bottle with an oak dowel on top. I had a beer fermented with just this yeast, and it was the bomb.