Those are large roundworms, by the way.
I do around 2 dozen birds every 3 months, it's not as bad as it seems. You can divide them into breed groups or age groups and do on different days if it makes it more doable, just gotta make sure you get them all. I close them all in the coop at dark when they go to roost, go out early the next morning before light and take them off the roosts one at a time and dose. You can get oral syringes at many feed stores, tractor supply stores, or any pharmacy (just ask). Shake the bottle well before drawing the dose (it settles out), pull down on the wattles, put the meds in the front of the beak .5ml at a time and let them swallow. Repeat until the whole dose is given. Turn them out into the run, and get the next one. If any struggle and freak out about being held, wrap them in a towel like a burrito to hold their wings. A helper can also be good, I generally do mine all by myself, no problems. It gets easier with practice. When your coop is empty, you have gotten them all.
For roundworms you need to dose twice, 10 days apart. The meds kill the worms but not the eggs, so the second dose is needed to get any eggs that hatch after the first dose, so the cycle is broken.
Roundworms are easily picked up in the soil while they are scratching and pecking around, so reinfection is common. You may need to worm regularly to keep them healthy. Some can do once or twice a year, some may need to do more often. Just depends on the worm load in your particular envrironment.
