As I added to my first post above, I kept saying "her" for some reason, sorry! I have never had roosters with crop issues unless they had heart problems/are failing at the end of their lives, probably treated two roosters in 19 years for crop issues, both they were in the state I mentioned, end of life systems shutting down, but quite a few hens. Hens tend to pig out a lot more than roosters, packing good on top of bad. I hope you can save him.
To touch on what azygous said, I do use stool softener gel caps for impacted crop. I use Gas X for a bloaty gas filled crop that is not truly impacted. Sometimes you have both, impacted that leads to soured. I have used the athlete's foot yeast cream/yeast infection treatment on a comb with favus, but not for crop issues so I can't speak to that. Sometimes, one thing works better than another depending on the situation and maybe even the bird itself and why it's soured in the first place. If it's end of life system shutdown, you can do all you can and it may not be successful. You'll have to try what feels right to you, lots of good experience here on BYC. I find that most chicken reference books never address sour crop. My Brahmas have always been prone to any crop issue they could drum up though they eat the exact same feed as the entire barn, all my other breeds. My Blue Orpingtons were the same. Crop issues are generally a symptom of something internal, though, not the primary issue.
A long time breeder and state tester for my state, Pine Grove here on BYC (William) once told me that tomato juice, salt free or low salt if you can find it, seems to help for crop issues, guess it's the acidity, same as lemon juice, but they like tomato juice a whole lot better, as you can imagine. He's been breeding almost as long as I've been alive, I think, and I generally take his advice to the bank.
So, lots of information for you. Good luck with your boy.
This is definitely where having a rooster used to being handled comes in handy. It's no fun treating one that completely freaks out when you take his feet off the ground, ugh. I've had one that did that, sweet as could be...until you tried to pick him up. Still sweet, never would bite, but he would flail around like a crazy thing and he was an armload. He hated losing control that way, while my huge Brahma rooster literally asks to be handled. Best of luck to you with the rooster-it will be a several day process most likely.
