Stick to one small rat a week for a few months. You can't go throwing food quickly at an animal that was starved for so long; their systems just aren't set up to handle that volume of food. Also even my biggest female breeder ball pythons are on medium rats, a large would be too much food for them.
You can also get a food bite from a critter that has been fed in its enclosure all its life. Just smelling the feeders thawing or scenting the room with live ones for 30 minutes is enough to get some of my ball pythons to come flying out of their tubs when I open them up.