Ball bearing rests on primer hole in shellholder. Grinding a small chamfer at the hole may be needed to keep ball centered (depends on the shellholder). Hey, they're cheap.
RCBS pocket swager die supports case from inside for ball-swaging and anvil-flattening steps. The body on mine, made for .470" (30-06, Mauser) cases, was too skinny for .495"+ 7.5 Swiss cases. Jam screw supports inner stem screwed below top for maximum extension, but it was also helpful to polish out the die body nearer to .495". Regular swager stud replaces shellholder and ball to flatten Berdan anvil and refine converted pocket. One "fringe benefit" of using the pocket swager to flatten the anvil is that it also compresses the Berdan flash holes.
Bushing improvised from small sleeve and a couple of short Allen screws centers drill on flattened anvil for Boxer flash hole.
Drill press and vise are shown here, but the guide bushing should work OK with a portable drill and some kind of improvised case holder. I used an inside flash hole deburring tool after drilling, but this isn't really needed.
A word of caution: some brass is considerably harder than the Swiss cases shown here - hard enough to damage the swager set, shellholder, ram, or even some presses. If you try anything that seems to be taking an uncomfortable amount of force on the press handle, stop there and try using Mr. Chandler's techniques which don't involve a reloading press. Berdan cases are expendable, good tools are not.