Most of the time the switch will happen without any problems. If you have a picky eater sometimes it helps to scent a rat with a mouse. (Rub the mouse on the rat)
Be persistent, eventually your snake should take a rat.
1.1 Columbian BCI, 1.2 Hog Island BCI, 1.0 Irian Jaya Carpet Python, 0.1 Ball Python, 0.1 Children's Python, 1.1 Amazon Tree Boa, 1.1 Dumerils Boa, 1.0 Horned Mntn Dragon, 1.0 Carolina Anole