I would refrain from giving any other foods except egg white. Picture a tidal wave of slimy egg white meeting the impacted string, lifting it out of the spot where it's lodged and carrying it on out. Other foods will dilute the egg white tidal wave we are hoping to set loose on that string.
Another analogy would be a clogged toilet. Simple flushing doesn't do anything since it lacks force. When I have a clogged toilet, I fill a three gallon bucket with water from the bathtub and dump it into the toilet bowl all at once, creating a tidal wave of force. It works every time.
This is what you will try to create with plain egg white. Flood his crop with egg white, a goose egg white would be great, or several chicken egg whites. This may be a bit tricky. I would either let him eat the egg white if he will or syringe the egg white directly into his crop, carefully noting when the crop is full and cannot handle any more. Trying to stuff more into the crop than it will hold risks overflow into the airway.
As for the grit, do not force that into him. Grit is something the bird will judge how much to consume by the way he feels. Just make it easily available.
Another analogy would be a clogged toilet. Simple flushing doesn't do anything since it lacks force. When I have a clogged toilet, I fill a three gallon bucket with water from the bathtub and dump it into the toilet bowl all at once, creating a tidal wave of force. It works every time.
This is what you will try to create with plain egg white. Flood his crop with egg white, a goose egg white would be great, or several chicken egg whites. This may be a bit tricky. I would either let him eat the egg white if he will or syringe the egg white directly into his crop, carefully noting when the crop is full and cannot handle any more. Trying to stuff more into the crop than it will hold risks overflow into the airway.
As for the grit, do not force that into him. Grit is something the bird will judge how much to consume by the way he feels. Just make it easily available.