Keep a blanket over the dog crate as well, you want to try and prevent her from laying another egg.
As for the other hens- I doubt it's something they'll get. My silkie who prolapsed was the only one out of the flock that did.
If the prolapse is no better tomorrow, soak it again and push it back in. Give her access to water, and some feed. I ended up needing to cut the feathers on her bottom, as I just couldn't keep the area clean any other way. The gunk, poop, and blood just stuck to the feathers like glue. Cutting them away gave me a nice area to work with, and it was easier to keep everything clean.
I honestly was ready to put my hen down several times but kept pushing as she was still alert/eating and drinking. I'm now thankful I kept trying and didn't put her down as it took me almost 5 days, but the prolapse ended up sticking and not coming back out.
Edited to add: The only thing I don't agree with in the other thread is the use of hydrogen peroxide. Coming from a medical standpoint while it does cleanse an area, it eats away the "infection" and dead cells, but also damages the living tissue. I wouldn't use something like that on a prolapse where you are dealing with an organ. I don't like using peroxide on simple wounds either- if I have to use it, I mix it 50/50 with water.