This is does not happen often but occasionally a bird will have a full crop full of stuff that won’t pass. Sometimes it is a lot of liquid, sometimes you can feel solids in there also. I have tried various things unsuccessfully on a series of birds and in each case. the bird became weak and died. Now I have had some success with a slightly unusual method. I had a hen with a crop full of liquid who was alert and moving around but not eating. I picked her up. Her crop was so full that as I picked her up, liquid came out of her mouth. I held her upside down and drained some of the liquid off. She was a sturdy hen of about 6 lbs. For a couple of days, I gave her about 5 cc of copper sulphate solution though a tube inserted down her throat, plus I gave her enemas of 50% BAM that I administered by gently squirting material into her vent from a syringe. My theory was that no fluid was passing into the gut and that I had to keep her hydrated in some way. The second day I added 100% BAM to the mixture I gave her orally. On day three, I decided to give her half a Vitamin C and BAM orally, and 50% BAM as an enema I thought the BAM would prevent the fluid in her crop from becoming putrid, and it did. I also thought that the bird would be hydrated from the gut. Apparently that worked also. After about 5 days, I was just about to give up, and I found the next morning that the crop had emptied and that the hen was getting a little interested in food. I continued the therapy for several more days until she was eating normally and I decided that I could terminate the treatment. Success of this kind is very rare.
Recently, I had a white silkie rooster with an impacted crop. I followed the advice I found on several youtube sites and gave him a mix of crumbled poultry feed, grit and olive oil. Then I would gently massage the crop 4 to five times a day. I put him in a cage with access to fresh water. I even brought him to the house and sat massaging him while I watched Netflix. On the morning of the third day, his crop had cleared and he went back to the population that hangs out in the horse barn. That was 3 months ago and the bird is healthy and active.