agree with the above. When we did ex layers some years ago, covered pen worked well, let them recover. We had good returns on them.In my experience there are positives and negatives...
On the positive side, they are cheap (sometimes free) they boost numbers on the ground and despite what I hear, I have found that if you put them into a covered pen for a few weeks they do hold ok.
On the negative side, they can come with disease so they need to be kept separate from your main birds so you can treat them without putting everything at risk. They tend to be lazy and not keen to fly or roost (sometimes the flight feathers need to recover) so mortality rate is high from predators etc ( another reason to use covered pens for them).
If you plan things right you can get your main birds early and the ex-layers late so they don’t cross over by much if at all.