I can't say for sure with your gubby, but I used to smolder the flakes between my fingers (so it gets very fine) almost like dust and then feed them with that. You should do that after you already fed your other fish normaly.
But again I am no expert so hopefully someone else will come here with and make sure what you can do
Crushing flakes works very well, but I have found that if there are no older babies with them, to show them that the little things floating above are food, they tend to take a while to readily eat it.
Freshly hatched brine shrimp are perfect for newborns, when the baby shrimp swim in front of them they instinctively eat them, and they will soon learn, when you come near the tank that means food !