I have tried three different ways of heating up and serving an F/T prey to my ball.
1) Prey warmed in water. The response was so so and the snake lazily took it.
2) Thawed in water but heated prey up using a heating pad. The snake started roaming his cage and had an aggressive strike.
3) Prey thawed in water but heated up using blow dryer. 20 seconds each side of prey. Snake was insane. When I opened the tub I had to be careful to keep her from going after the prey before I could offer it to her. Her strike was very aggressive.
Over the course of a month I repeated each type of offering. I have concluded that the pre-scenting that the blow dryer gives puts my snakes into almost a ferocious predatory mode. You would think they were starving by the way they start smelling and trying to get at the prey through the tub. I scent it right next to the tub and so far every week she responds the same.
Even my baby Dumeril who will not even look at a F/T or a live for that matter when I am in the room is driven to roam and smell when I am scenting....
So you may want to try using the blow dryer approach. I think it is superior to any of the other methods I have tried.