This is a good time of year to do it, because most ball pythons are putting on weight before breeding season. Though sometimes moving to a new home with trigger a fast, and if that starts, I'm just thankful they eat anything.
But once you've got them eating regularly, I find leading with a small live prey and following with a warmed f/t as a second helping works pretty well.
And if that doesn't work right away, it's just persistence persistence persistence. Older snakes like this one can be pretty set in their ways. So I won't starve them, but I'll only fed them a single small live prey item every two weeks or so. After they eat that, I'll dangle a nice f/t in front of them. Look what you COULD be eating! No? Too bad. I guess you only get the one little mousie today.