Congrats on the prey switch. I know from experience that it can be a pain in the butt.
Here's a suggestion. If you have to feed live prey, keep something like a pencil with you while feeding. After the snake constricts, you can quickly slip it into the rat's jaws before it gets the chance to bite your snake. I have done this and it works great. My little guy Ashes is flatly refusing to eat prekilled prey, but will gladly take a live large mouse (he is not big enough for rats yet.)
I am not a lover of live-feeding, only in hopeless cases. Ashes was off-feed for a month while I tried feeding prekilled; now he eats weekly. But it can be messy, is a general pain, and I greatly prefer my snakes who'll eat prekilled.