If you pull a rat out and just give it a few hours to sit there it will be thawed completely. If your not sure its thawed, have it in a baggie and gently squeeze it a while and see if you can feel any coldness. If you cant, its good to go. Then just warm the head with a blow dryer a little so that the snake has a proper target for its heat seeking jaws and there you go. FT is so much easier to deal with. You can buy in bulk, store, and you don't have to run out to get another. No fuss, no muss, easy peasy.

On a side note, never seen a snake injured by a dead mouse, unless you threw it at them frozen. Then you could put an eye out.