Babies usually won't start on anything that isn't moving. A mouse fuzzy/hopper is the best thing. Pinky is much too small and doesn't move. Plus they really need to be in a small small enclosure.
Most of us keep hatchlings in a box no bigger than a shoebox. They feel secure.
When assist feeding, you should use a pinky so it goes in easily. Do not force feed. Just get a prekilled or warm thawed pinky wet and put the head in the snakes mouth and push it as deep into the throat as possible. Then put the snake down quickly and then sit very still and wait. The snake should begin to swallow. If it spits it out, try again. If it spits it out again, wait a couple days and try again. It will eventually swallow that mouse. After a few times you'll kick in the feeding response and it will readily strike and take a fuzzy/hopper sized mouse. A few weeks of those and you can go up to a larger hopper/weaned size or a rat crawler.