I do anywhere from 25 to 100 chickens a year. By hand it takes me a couple of hrs to do 10 birds. With my plucker I can do 50 in a couple of hrs. It's well worth the money for me. I have better things to do than pluck chickens all day.
Everything you want to know is right here: https://www.backyardchickens.com/threads/graphic-pics-of-my-day-learning-to-caponize.675898/
I've done probably a dozen now at 3 months old. The testicles break easier the older they get. But there is no difference in doing it at 6 weeks or 3 months.
I've tried a lot of heritage meat chickens over the last 7 or 8 years trying to find something that grows a decent sized breast and will weigh at least 3 pounds dressed at 16 weeks. And the closes thing I have come up with are 3rd generation hatchery stock white rocks. You have to breed the...
I have found white rocks to have a bigger breast than any other dual purpose I have raised. They don't have a huge breast like cx but it isn't super skinny. They are also one of my favorites to fry.
I like to butcher at 14 - 16 weeks. After butchering I let them rest in the fridge for 3 - 4 days before putting them in the freezer. Most dual breeds at this age will be 2.5lbs or so dressed.