I learned this from VPI and I got three stubborn females to switch to f/t...all on the same day! I call it "peek a boo". Warm the rat up really well. Then grasp it behind the head with forceps and put it behind the water bowl or hide if you have one. Have it "peek" out and as soon as the snake tongue flicks, have it go back behind it's hiding place. Do this several times as the snake builds more interest. When the snake appears to be in full feed mode, have the rat "hop" over in front of the snake. This has worked wonders and after a while, I didn't need to do it anymore.

Another trick I have with a snake that really is more of a mouse feeder is I take a live mouse in one hand dangled by the tail with a f/t rat on forceps in the other hand. I let the snake see the mouse but keep just outside of strike range. Once she is really interested, I let the mouse crawl all over the rat to scent it and then put the rat in front of her. This is absolutely the only way I can get her to take a f/t rat so whatever works.