I feed live myself, but the best way to thaw would probably be to put the mouse in a sealed bag and place it in warm/hot water (not boiling). I've heard others say they have to dance the mouse in front of the snake, while others yet just dangle it in there and the snake takes it readily. Also, maybe leave the F/T mouse in the enclosure with your snake undisturbed and see what happens. I'm sure it takes alot of time and patience to make the switch though.