I find the easiest way to get a reasonably accurate dose into each hen is as follows;
Measure out 7 eggcupfuls of mixed corn, or corn + hulled sunflower seeds, per hen. Put about 1/4 of the total into a large container and add cod liver oil, or sunflower oil, to coat the pellets. Add the correct amount of Flubenvet powder for all the hens, stir very well. Gradually add the rest of the corn, stirring as you go.
Feed one eggcupful per hen, every day for one week, as scatter corn at 'treats time'. Separate any very greedy or dominant birds, or any who get bullied away from treats, and feed them separately. You will see that every bird is getting her dose and it will all be gone in avery few minutes. You will have mixed exactly the right amount to last the week, and won't have to worry about whether they're getting the right dosage. No waste from surplus food, and the hens will love it!
Stuff like Vermex etc may well be a valuable tonic to keep the hens' gut in good order but is NOT a complete or satisfactory wormer. (Have a look at the thread on the Chickens Health section of this forum about the relative effectiveness of other wormers and Flubenvet.