Snakes will not associate the hand with feeding unless the only time you open the cage is to feed. Lately, I only take my snakes out to feed, so they associate coming out of the cage with feeding and they go into feeding response the minute the door opens, so feeding in the cage would probably result in less bites for me. If you think they will bite while transferring from the feeding box to the viv, wear some smooth leather gloves. My Okeetees stay in feeding mode for quite a while and will grab onto whatever comes into the box so gloves work well. They also reduce the heat signature and although corns don't really use heat to hunt, they do recognize a heat signature and if they are still feeding, they'll strike at it. Unless you have paper as a substrate though, it's best to feed off the substrate.