The only Berdan primers I ever fooled with were in some Kynoch .450 Express belonging to a friend. We clamped the sizing die in a vise, mouth up, and dropped a case into it. Then drove a common awl through the indent at a sharp angle so as to miss the integral anvil and just levered the primer out of the pocket. The same principle as the RCBS device, just with ordinary tools.
You can do it with hydraulics like Mike40 describes, you can even do it on the press with an expander plug. It is possible to bulge the brass beyond use if the primer is crimped or corroded really tight in the pocket.
res45s video does not emphasize it, but uses a balanced hydraulic surge that won't hurt the brass. There was an old Gun Digest or Handloader's Digest that showed a fancier set of tooling for the same job.
Getting into trivia and history, once upon a time, British shooters could support a domestic reloading tool industry. There were three Berdan decappers operating on completely different principles.
The Prime Hydro Punch had a water reservoir with plunger and a long nozzle that reached down into the case and set over the flashholes. A whack on the plunger forced the primer out with hydraulic pressure but with only a couple of drops of water released. Lots less messy.
The Prime Power Punch looked similar but the long nozzle set a fresh primer down against the flashhole from the inside. The exposed plunger was the head of a firing pin and a hit on it blew the Berdan primer right out into a shielded base. It cost you two primers per shot, one to shoot, one to decap, but was quick and dry. You could use a more common Boxer primer in the decapping operation. Noisy, though.
Prime or maybe Wamadet made a decapping spindle that went in the sizing die like a regular Boxer decapping assembly. For Berdans it had an offset decapping pin made of fine but strong piano wire. You left it loose in the threads and as you raised the press ram, mainipulated the head of the spindle to feel the pin into one of the flashholes. Then pull the press handle to decap like Boxer. Said not to work with crimped primers, the fine tip would just punch through.
But all that was in a bygone day and the old British tools largely forgotten.
I looked and the Wamadet seems to be back in production, but Prime is apparently long gone.