For any blister, I would definitely drain it. Try poking it with a needle to open it up. Then just press on it with some gauze.
We all know your chickens are far from ill managed. They probably have outdated info in that book obviously they can get it another way.
Also if you cam coco butter has always worked good for blisters. Might be kind of hard to get that through here feathers. But if you can it might help once you get the blister drained.
I hope its nothing serious.
Thats great! The more people who can jump on board the easier and faster we can get some better feed.
I am going to start a sub-thread for this Cascade co-op feed drop to keep all the information in one plac if noone else wants to???