Have you tried chain feeding? (feed a small mouse first, then while he's still pumped up, a small rat pup; just make sure the 2 combined are not too big of a
meal.) Some snakes will ACCEPT the second rodent but BPs can be difficult -understatement- so what I've done is be as still as possible but be RIGHT there
with the rat pup on tongs & with subtlety, introduce it into the snake's still-open mouth, rat nose to mouse tush. If you are too pushy or obvious, your BP will
probably hide his head or spit it out, but if you can manage "sneaky", some keep swallowing & learn to accept the new taste as edible this way.