How to win the fight:
First, I don't think making them go hungry actually helps much, if at all. Repeated exposure seems to--many won't take it on the first try, but will take it a few tries down the road...regardless of whether they've eaten other things.
1) Heat the rodent up extremely well. Use hot tap water--be sure it's not so hot it will burn, but it should be warmer than a normal live rat.
2) Wiggle it. A short back and forth motion seems to get their attention best.
3) Worst comes to worst, rub it liberally in the pee spot from a live rat--get it good and stinky with rat pee. Apparently, frozen rats don't smell like live ones, and stinking it up with rat pee disguises this. Same trick works with mice, and also to switch from mice to rats.
If the meal is rejected, give up, offer a live rodent, and try again next week.
I had one adult female take THREE YEARS to switch. I offered her FT every time I offered it to my other snakes, and she gave me dirty looks, and would only eat live. Then, one day, bam...she's taken them ever since.