I use Berkey filters, and I don't think there is loose charcoal inside.
I looked up a video, and he didn't find loose charcoal either. The black stuff is solid, and is the filter element.
I made my own drip system out of big commercial food storage tubs, the things restaurants fill with stuff like potato salad so it can be ready. It uses Berkey or Doulton filters, I'm currently running Berkeys because I need to use the fluoride filter also, and it hooks on the end of a Berkey but not a Doulton. The stainless steel system Berkey sells would be spiffier, but mine was cheap, and works for us.
As far as reworking a Berkey, I'm not sure it can be done other than to clean it well.