I was having problems feeding F/T to my ball pythons too. I was told a few tricks buy some fellow reptile owners. First, when feeding f/t put the rat or mouse in a plastic bag or two and put it in a big bowl of hot water. Next put a smaller bowl of hot water on top to submerge it to thaw. I usually wait 15 to 20 minutes before i take the mouse out. After the time has passed i take the mouse out and set him under a heat lamp. I use a 100 watt heat bulb. I let him sit till he's warm to the touch( i know its a little gross) And completely dry. The next step is really IMPORTANT: Move you snake to another tubs. I use a spare or empty tub. There doesn't need to be anything in it. The reason for this is that if he's still in his home he will respond defensively to movement/new prey being offered. I take him to a fairly dark room. In my case the kitchen with only the heat light on. I let them sit there for a minute to relax then i try offering the mouse. Its worked 100% of the time for me.
Edit: I also recommend feeding in a separate cage because hides and substrate can be health hazards. Most hatch lings do better when fed in separate feeding tubs.