Make up a swaging button for your press. It's only a few thou and the brass moves quite easily. It tends to want to "spring" back a bit though.
I've only had to do this once, with some 8mm Kropatschek milsurp brass.
I have two different sizes of primers, one from North Silva, on special order and another from Canada Ammo (Dominion)
I tried swaging the pockets in my Rock Chucker, but tore off the rims or deformed them.
I finally made up a hardened pin and inset it into a 6''x6''x1/2'' steel plate.
Then all it took was to position the primer pocket over the pin and insert a brass rod into the case mouth to whack with a hammer.
I went through the trouble of drilling out and profiling the pin to approximate the shape of the anvil on my cases.
It's nit picky but simple and it works.