I had a fairly young hen with prolapse several years ago. Her eggs were huge and more round, than oblong.
I read up on it, and it was stressed that she needed to be forced into a molt, and to stop laying if if were ever to heal, so I brought her in the house, used the Preparation H pushed it back in, kept her in a dark place, reduced her feed to only scratch grains. I had to help get those last couple of eggs out of her. After a time she healed, and I put her back with the other chickens. She started laying again sometime later, and after each egg, you would see that she had prolapsed again, but within a short time, (minutes) it would go back in on it's own.
I hope that helps. This happened maybe 8 or 9 years ago, so I don't remember specific details anymore.