I personally don't feed them anything extra. They quit laying so the protein that used to go to making eggs now goes to the feathers.
Some extra protein won't hurt as long as you don't get ridiculous and overdo it, but mine always grow bright, sleek, shiny new feathers back without a lot of extras. Extra protein might speed the process up a bit. I don't know how much protein their bodies can process and use, but it sounds logical that extra protein could speed it up.
One of the few things I am confident of is you won't hurt them by not increasing the protein as long as they are getting a decent diet already. Extra protein when they are molting is not something you have to do. More of a personal preference.