I will start by saying i don't know anything about kings, but i do have a few ideas and tips that work for other species.
this could help you out..
for nocturnal hunters, you want to handle day time, wake them up, guide them out of the cage and then once in your hands, they may calm down and be curious.
just don't do any quick movements in front of them or do anything that can startle them.. always from behing/under.
handling them day time, will associate handling day/feeding night patern
for agressive snakes that feed anytime of day. you could use the snake hook training that we use with reticulated pythons..
in order to switch off the feeding response, you gently touch them on the head with the hook, then carefully take them out of the cage..
if yours is really nippy, you might want to practice using a snake hook on a regular basis.
use it as part of your routine.
unfortunately, some snakes are always that way.. if young it could be a simple defensive reaction still, in time it may relax and get use to you..
best of luck