i have a speckled Sussex, Ruby, who is almost 2 years old.  She has a history of sour crop and pendulous crop, For a while, we used a pair of toddler underwear with a hole cut in the bottom to lift and support her crop.  She was occasionally getting her foot stuck, though.  This is the worst she’s ever been, and with the gas, she was at risk of aspiration when we would put a bra on her.  We tried Monistat, but after 2 rounds it wasn’t working.  We were afraid we would have to put her down, but decided to spend the money on a last ditch effort.
We are using Simethicone, nystatin, and a molasses flush.
 I just gave my Ruby simethicone (Gas-X).  I used the adult human form, but used a needle to pull the liquid out.  You have to puncture two holes and I used a 16g needle.  It was a minute amount, but made a HUGE difference with her.  I think baby Simethicone would be easier.  I couldn’t find any information on its efficacy or toxicity, but I took the risk, as she was going to have to be put down instead.  We just did this about 60 minutes ago, so we will see what happens ultimately.  She was so filled with gas that it took up more than 60% of her horribly distended crop.  I wish I had taken a before and after, but she was so bad, her crop nearly touched the ground. She now looks like a bird with major pendulous crop, a huge improvement.
My daughter gently massaged her crop 15 minutes after administration and she was able, over the course of the next 45 minutes, able to greatly reduce her crop size.
She has sour crop and pendulous crop. 
When she finally had room, we slowly administered nystatin for birds (
https://birdpalproducts.com/products/fungistat-powder) that we had diluted with molasses flush water.  We also bought infant bird formula and mixed it with yogurt.  She has been left with this in her cage along with molasses flush and fresh water.  She started pecking at the yogurt formula feed.  This is the only nutrition she seems to finally be eating.  Hopefully this will pull her through.  She is isolated in a crate on my 3 season porch.
Honestly, I think the Simethicone has made such a huge difference that she can actually make room for nutrition.  It’s important to get the nystatin in her, too, so that she can actually rid herself of her problem. 
hopefully this will work, but I wanted to post what I had done so that if it works, or doesn’t we can let others know what we did and learn from it.
The first two pics are her after treatment today.  The last is her in her “normal” state of crop.