You ought to go out in the coop(s) early in the morning before sunrise with your flashlight and snatch them off the roost and worm them one by one. It's much easier because they cant see in the dark.Ok. They all got their first dose. Holy crap they were hard to catch. I have 24 and the last 7 gave me a good workout. I checked their poop from last night and a few poops had worms so I'm just treating them all. Will repeat in 10-14days.
More importantly, they will have an empty gut because they havnt eaten yet and will be hungry, so will the worms. The wormer will be more effective eliminating the weakened worms. You might even see pieces of the actual tapeworms excreted within an hour after worming. Otherwise it'll be digested as protein.