You may want to consider getting long feeding tweezers or feeding tongs to hold the rat with when introducing it to your snake. If you're holding the rat by the tail you have rat scent on you. If your hand is a wee bit warmer than the rat . . . kapow!!!
It doesn't really hurt -- it's more startling than anything. And it's happened to a lot of us on this forum. But the danger can be minimized by NOT using your hands to present food to your snake.
<><Peace