Not sure what he uses but I've had good results with Black Oxide solution from Caswel Plating. It blackens the hardware but it doesn't protect it from rust. You need to seal the fasteners after they are darkened. I've used RPM from ECS but lately I've been using Johnson's Paste wax. Heat the part with a heat gun or torch and brush on the wax.

I have a Harbor Freight tumbler. I think they say you're supposed to use them "dry" but I didn't have good luck with it "dry". I like to use it with a little EvapoRust or a degreaser. With heavily rusted fasteners, the tumbler + EvapoRust seems to get the job done quicker then just dipping them in EvapoRust. With small grimy fasteners, sometimes it can be easier to tumble them with the degreaser instead of trying to clean them individually. Make sure you keep an eye on the tumbler though. My Harbor Freight tumblers motor locked up once. If I hadn't caught it, things might have gone bad. I was able to free it up so now I only use it when I'm out in the garage and can keep an eye on it.