Rolling the f/t rats around in freshly used poopy mice aspen (you can ask for a bag at some pet store) also gives a fresh, strong scent and seems to help a lot for me, so it's worth a shot.
I literally get a dirty bag of it and save the stuff for months to use for scent coating for every feeding. I just have one problem snake who hated f/t, but he's been eating consistently now. If I don't roll the f/t rat in the smelly mouse aspen though, he won't take it.
Good luck!