Some will take f/t, others never will. If the animal has a strong feeding response, it is much easier to get them to switch. If they are a reluctant eater, it may be virtually impossible to get them to switch. I have one adult male that I will never get to eat anything but live mice. I have resigned myself to this fact. Some simply won't respond if you are hovering over them doing the zombie dance with the rat, and they may be unlikely to take the rat without the motion to entice them. The best advice I can offer with regards to that is to feed them live and don't handle them often or at all for a few weeks. Wait until you get aggressive feeding responses. Then try dangling the live rat over them for a feeding or two. If they take the live rat off the tongs, try an f/t the next time around. At that point, a rat dangling over them is not so abnormal and they are more likely to take it. At least, that has been the case in my experience. Good luck!