FWIW I usually make sure the snake has struck at the first and then put in the second usually almost immediately after. I have to do it differently for my two snakes, as their behavior differs.

One pretty much always stays in its hide in the middle of the enclosure, so I just plop the rat in front of the opening for that and it'll take it.

The other is a little pickier but also more adventurous, so I make sure to leave the rat on top of a hide directly under the heating element so that the rat stays warm. She moves around the enclosure enough at night so she always finds it, whereas the other wouldn't.