I have had an issue twice in my time and read on byc, to do exactly samething, flip them upside down and massage there crops and get there crops empty, well in my case, it ended up killing my silkie, I will never do it again. But it happened to me with another chicken, contact my vet and he said do not flip the chicken upside down, it's a last resort and way to risky. So he gave me advise on other ways of handling it and amazing that chicken is doing well and still with me..I am glad you did. I am learning something about sour crops from you guys never dealt much with it. I don't know why I never have chickens with it. Maybe it is because I free range them.