It sounds like you did a good job, I would make sure she drinks alot to help flush her system. Maybe someone else has better advice!
Thanks for the support. I'm off to sleep but we'll see what happens. I read some more about what to do if it were a person or other mammal since I couldn't find anything specifically about poultry. I also eventually reached the poultry vet who felt that washing was all I could do. I'm making the notes below in the unlikely case anyone else ever does this:
Usually the advice is 15-20 minutes of flushing with cold water but since I figured that would also be bad for a chicken, I opted for a second bath in warm water + dish detergent. I was out of foam Dawn so I used liquid Sunlight, which I normally prefer anyway. I put her in a bucket of warm soapy water for even longer than before and swished it to get it around her skin, especially places I knew I'd sprayed. (I imagine one long bath is fine, but if the water is cooling, then dumping it and preparing a second bath I think would be better.) Then I rinsed her in the bathtub faucet as well as I could.
After the longest and frankly most challenging part: drying a sopping wet chicken. Seemed like it took about an hour with towels and a blow dryer. It was about... +26C I think? But the breeze felt cold, so I was trying to keep her in the sun but warmed and fluffed with the blow dryer.
Whether it was the chemicals, and/or wet & cold, she seemed to be having trouble walking for a while. Alert, good appetite strong grip with her toes - but her coordination was off. She walked a bit like a duck. After she was dry she wanted to be in the shade. I left her there for a while and then after maybe an hour moved her into a sunny spot. The warmth helped, as did her flock-mates perhaps. As of this evening she was acting pretty much normally but we'll have to see.
I'm assuming there are two dangers:
- The neurotoxin
- The petroleum distillates used as a carrier
The latter I'm guessing may take a day or two to manifest. Merck's page said that PDs used as a carrier isn't a big concern, but I don't think that was a poultry specific article.
Bottom line:
Don't spray your hens with wasp spray!
