I drilled a hole in the table of my table top drill press. This hole is large enough to accept the pin punch. I lay the poured jig on the table and insert the pin punch. The drill mechanism allows me to apply firm steady pressure and a stop to keep from over opening the eye. This works well, but you stil get the occasional broken eye.
I also found that if you heat the eye if a black nickle hook to a cherry red it will allow it ti open easier. This does not seem to affect the strength of the eye and have not had one fail so far.