What i did with my live feeders when i was trying to switch them to F/T is leave a couple live rats in a plastic bin above the enclosure or rat for about 3-4 hours, then i would thaw out the frozen rat (making the head warmer than the rest of its body), scent the thawed rat really well with a live rat, allow the snake to strike and coil then move the F/T rat around for about 30 seconds so the snake believes the rat is struggling - usually the snake will take the rat without an issue. However some snakes are set on live rodents and wont take F/T regardless, but most will as long as you stay consistent and continue offering F/T.