A pinky pump is essentially force feeding. The idea is to get your snake to learn how to eat, and you can't do that with a pinky pump. Assist feeding entails getting a hopper mouse or small rat pup and placing the head in the snake's mouth. Close the mouth over the mouse/rat and give a gentle pull to catch the snake's teeth in the skin so it is more difficult to dislodge. Then wait until the snake is calm (as calm as a snake can get that you just shoved something in its mouth), and place it in its cage. If the snake spits it out, try again. You may have to do this several times until the snake starts to swallow. It can take a lot of patience depending on the snake.
I've never used a pinky pump, but I can imagine that you would only use it in dire circumstances where the snake is too weak to eat or is unable to be assist fed after many, many tries.
In any case, I think you have a little bit of time before attempting assist feeding. Keep a close eye on your snake and if you notice it getting thinner or weaker, try to assist feed. I would follow the other suggestions in this thread in the mean time. Don't wait too long, though. Baby snakes can and will starve themselves faster than larger/older snakes. Plus you run the risk of their digestive system shutting down so even if you do manage to get food it him, it may be too late.
Good luck!