Why caponize?
If I may jump in here, there is also a product called Solarcaine, used for ON the skin. Similar 'cains are used in tattoo parlors to help numb the skin before piercing it with needles. It does provide a brief numbing of peripheral nerve endings, but does not provide any anesthesia - only analgesia.
Anesthesia: unconsciousness, reversable, amnetic (no memory), no sensations. Isofluroane, Halothane, Sevoflurane are anesthetic gases used post a pre-anesthetic drug, often propofol or ketamine (at least in veterinary medicine, I cannot speak for humans). Must be used with vaporizor and oxygen and highly trained person(s).
Analgesic: reduction of pain by inhibiting nerve receptor functions either peripherally (limbs etc) or centrally (spinal/brain); COX inhibitors, Opioids, etc are examples. Oral, topical, IV, IM, subcutaneous, there are different routes for these type of medicines.
SO, the whole reason for this forum - thread is to educate each other on what we have found works, what is the quickest and most painless and most effective method of dealing with roosters we cannot keep. I for one am allowed up to 4 roosters on my property. That's even a lot when they're all crowing at 3:30. BUT, caponizing ALSO stops these birds from fighting and crowing, so they can be housed together. They become gentle and make quite docile pets. I would rather sell, or even give away, my hatched roos as capons and ensure they will not be used as pit bull bait or as fighting birds, as illegal as it is it occurs here, or be able to find them homes as pet birds in more surburban areas where they are no more nuisance than a dog. For me, it's more a question of owning a stallion or a gelding - you can find a lot more homes for geldings than stallions. Not all stallions should breed. Geldings make better "pets" or mounts. Same with roos. I don't kill any of my birds to eat, even my old biddies, at least not myself.
Frankly, I DO stitch my birds' derma after an incision. It aids in healing by first intention, reduces the chances for infection, bleeding, puffing, etc. I am certain the birds feel something, but animals do NOT perceive pain the way humans do - we are big sissys and they are not going to let it get them down. I am not advocating tying them to a chain and dragging them along the street by the bumper of a car, letting them fight until one bleeds to death or gets infections which are painful, slow, and lingering, often followed by isolation from the flock and death, nor do I wish to enjoy the experience of caponzing. This is a practical matter, and this forum seeks to find the best way of doing what we have to, want to, or need to do.
I breed my own replacement hens to supply quality eggs to many many people, in thus reducing my c. footprint and theirs, by not buying caged hens' eggs, having them shipped from Thailand, waste grocery store space, etc. When I incubate, some are going to be boys. I raise them with care like the pullets and then do the best we can to get them an overall normal life followed by a QUICK, if any, death. Take a moment to think about what happens to the other half of all the egg layers raised in this country (MILLIONS) - they are disposable lives, piled into boxes to die without food or water, comfort or care. IF raised, by the time they're 16 weeks they can't be eaten and are discarded like trash because they aren't large enough for American appetites. I prefer my way, the Homesteader way, and if that means a cock has to lie still for 15 seconds of discomfort, that is a lot less discomfort than I spent in college learning anatomy, pharmocology, radiology, exotic medicine, parasitology, laboratory medicine, surgical nursing, and nutrition, among other stuff.
If you can't contribute to this thread positively, with a way to "make it better", then you may want to examine other back yard chicken threads for what you are looking for - coops design, feeding, incubating, mail order, etc.