Assist feeding is just one of those skills you eventually develop if you have baby snakes. With the history on these two I probably would have started four weeks ago given their low birth weight.

From my experience:

Trying to assist feed mouse pinkies alone is worthless. As I'm sure you discovered - and not to be too gross about it - they fall apart during the process. They're not stiff enough to be useful in getting the snake's mouth to open up, so it can take a few minutes to get the pinky into the snake's mouth. Once you do get that done, if the snake puts a few teeth into the pinky and breaks its skin, the pinky turns to mush, the snake spits it out, and you have to start over.

There's a much easier and less stressful way of getting the job done. With a bit of practice it should take no more than a few minutes per snake.

Warm up one f/t jumbo mouse as well as the feeders for each snake, usually mouse pinkies or fuzzies. Cut the hind legs off of the warmed jumbo mouse, the same way you would if carving the leg/thigh off of a roast chicken or turkey. If you angle the knife right you can even remove some extra skin/fur from the mouse's side. Feed off the jumbo mouse body to something else like a king snake in your collection.

Once everything is ready, pick up one of the jumbo mouse hind legs and fold it so you're holding the toes and cut end in your fingertips. Push the folded hock joint into the snake's mouth; the cut end and the mouse's toes will go in last. It's easy to pop the snake's mouth open since the leg has the femur in it that you can use for leverage. The leg is hard for the snake to spit out if the hock joint is in first, as it wants to flex open, so it catches behind the snake's teeth. You can also push on the femur bone a bit with your pinky to move it along once it's in the snake's mouth, though this is a good way to get bit. The leg goes down easier if it's damp.

Watch for the snake to start swallowing the hind leg, and have the whole prey feeder ready to go. As soon as you see the leg going down the hatch, sneak the feeder's head into the snake's mouth while it's open. Don't try to force the feeder down the snake's throat, just support it while the snake is eating the mouse hind leg. Eventually the snake's teeth will grab the feeder and it will get swallowed as well.

Repeat weekly but give them the opportunity to eat their feeders on their own before assisting. Also look for other signs of food response, like wrapping the feeder once they have a hold of it, that will let you know they're getting closer to eating on their own.