OK, kids, let me tell you what I know. My Black Australorp, Naomi, had a recurrence of sour crop. Her first experience was on Jan 9. She returned to her "home" on Jan 14, so it has been about 10 days. I brought her inside last night and by this morning, her crop was still quite squishy and about the size of a tennis ball. I had tried to vomit her when I brought her inside but to no avail. Even though we have good info on this board, I decided to take her to a local vet who has a specialty in poultry. Since she just had a round of this, I apparently wasn't doing something right. Naturally, by the time for her appt. came around, I could tell that she was beginning to be better. Her crop was smaller and she was pooping. I decided to take her anyway just so I would know.
He did an aspirate of her crop and identified some yeast there but not as large as I had expected. He comfirmed that giving her soft foods and ACV vinegar (16ml/Liter) is the right thing to do. He recommended doing this for 3 weeks to give the crop a chance to heal itself. It is a smooth muscle and if it gets a "pocket" in it due to being enlarged, then that would not be good. I will need to keep her separate from the others so that she can have the soft foods and ACV. He didn't recommend giving all birds the ACV because it could change their pH.
He tends to think that the pine shavings that I use for bedding may be the culprit for her problem since I haven't changed her feed or made any other changes. I am going to remove those tomorrow and put in sand. He said that sawdust would be an alternative since it has smaller pieces but I don't know where to get any of that and I have sand down at the creek.
When the crop is squishy as opposed to being hard, do not give any oil since oil and water won't mix so it won't do any good. If the crop is hard, then oil may be effective.
I got a catheter and syringe from him to draw out any liquid should the problem recur.
I don't know if this info is helpful to anyone here but I wanted to post what I had learned. I don't know if I would've come up with the pine shavings as being a problem so I'm glad I went.