With wry neck I would give 400 IU of vitamin E daily, along with some thiamine B1 which is in the NutriDrench or in 1/4 tablet of B complex vitamins. A little scrambled egg daily has plenty of selenium which helps the vitamin E uptake.
Since wry neck is just a symptom, it can be from a head injury, a vitamin deficiency, or sometimes it is seen in certain diseases, such as Mareks and a few others. I would treat at least for 2 weeks. Sometimes it gets better, but in some cases it may not. Getting them to eat a very wet mash of chicken feed, water, and scrambled egg bits several times a day may be necessary. Here is a video: