Make sure it's really warm, and you can always put a live mouse in with it just before you feed, to get the mouse scent on it.

Try wiggling and making it "walk" around by it's tail, I find this works better than trying to make it look real by using the back.

Maybe try a F/T mouse first before a F/T rat.

Sometimes they just don't take F/T after too long of having live prey.

Good luck!