First step, get them used to eating off of tongs--dangle the live fuzzy from the tongs for them a few times.

Then, use scenting over. FT rats smell nothing like live ones, and it can be as challenging to get a snake to accept them as it is to get them to accept a different species of rodent.

Rub the thawed, warm fuzzy in soiled rat bedding, particularly in rat pee. This will give it the scent of the live rodents. Make sure the fuzzy is VERY warm when you offer it--above your own body temperature. Make it move convincingly with the tongs--not too fast or violently. Practice will help you figure out what triggers the snake's instincts best. After the snake has eaten scented ft prey a couple of times, they generally don't need to be scented any longer.