Often after unscrewing grub screw that hold detonator pin, it will go out by itself.
A few times I used thin pliers to grip pin and pull it out, but this is a bad idea - too easy to scratch pin.
My latest invention is a bamboo chopstick, split in half with a knife. It is thin enough to fit beside the metal, and it has a good shape - externally rounded, flat on split side. This is enough to push pin through the barrel.