Hello, and welcome to BYC! We're happy to have you with us! 

Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Short answer.. Working as quickly as possible. This may surprise most people but THE SECOND they are released back on the ground they go back to normal behavior. They don't seem to be phased by it after the fact. But also remember I'm doing this at between 3-5 weeks when there's a lot of room in there to not have to displace hardly anything to get to the testicles.I've been curious about caponizing since we are doing meat chickens. I can do surgical stuff but feel a bit squeamish about operating on a bird who I can't give an anesthetic to (or isn't on death's door and is going to die anyway.)
Did you ever source the chemicals for chemical castration? Or (and I have seen videos) simply doing the back cuts for the testicles was fast enough that hopefully they weren't in a ton of pain?
I've watched videos of birds having impacted crops cut open and largely they hold their pain so well.
And I also know that if it's culling a rooster versus caponizing and giving them more months of life they would probably choose the extra life, but still. Has there been stuff that has worked for you to mitigate pain, or simply working as quickly as possible?