I was going to add to this but I think the answers already given cover almost everything I would have said.
One point that is worth adding though is not ALL ball pythons are picky feeders - far from it in fact. So you may be worrying unnecessarily.
I feed slightly smaller meals ( small rats or even large weaners most of the time ) and I've found this reduces the amount of refused feedings. The biggests parts of this trick is to find how your snake wants its meals presented and to let it defost near the enclosure so the snake knows a meal is about to be presented ( I only feed F/T ).
I'm ok with wasting a bag of frozen/ thawed rats to see if I can find a way the animal will accept the meal than cause pain and distress to animal I'm about to drop in the same enclosure as my snake.