Hi Rocky, for a really dirty carboy, especially if I don’t know it’s history, I use Five Star PBW Cleaner. Use hot water and let it soak for about 30 minutes, then hit it with a drill mounted carboy cleaner. It works miracles.
Here is an article by Daniel Pambianchi
Here is an article by Daniel Pambianchi on acid adjustments that might be helpful: Acidification/Deacidification - Daniel Pambianchi