It is so easy, cheap, efficient and fool-proof to use a jack-knife, that it has always been a wonderment to me why anyone would use any other method. I even cut a two-year-old bull quite a few years ago. He survived and made a lot better looking steer than he ever did a bull. :? On calves we slit the bag. On older bulls, we cut the end off for better drainage. We pull out the testicles all the way. Sometimes you don't even have to use the knife to sever the cord. When cutting the cord, it is best to use a scraping motion with the knife blade which lessons the chance of bleeding.
Back 25 or 30 years ago, there was an ad in the livestock publications promoting a vaccine for castrating. The idea was to give this vaccine injection into the scotum and it would shrivel up the testicles turning the bull into a steer. Our neighbors tried this at branding time and had a wreck. Evidently so did everyone else who tried this miracle treatment, because the product was no longer advertised after that.