For me, I keep ACV (raw with mother, plastic containers only) pretty much all the time in the waters. Then have good feed which contains prebiotics and probiotics and balanced nutrition.
I then *try* (though I admit I forget) to put out a home brew of Molly's herbals (which includes wormwood that has shown to paralyze and expel worms) in a mash with garlic (fresh best, but I also use powder), pumpkin seeds, and cayenne. I blend that up in a blender, choppy looking, smelling like an Italian restaurant and looking noticeably "rusty." The cycle is 3 days every 6 weeks as the wormwood can be toxic. I probably do that about every 2 months (that 6 week thing keeps blowing by...I can remember months better, on the same day). My birds aren't always really keen on eating it, but I do try to remember to offer it to them.
Before Hygromycin B was taken off the market, I would worm with those pellets twice a year in fall and spring for a week as it was FDA approved with no egg pull time.
Since Hygromycin B is off the market, I now am using up some Ivermectin before it goes beyond pull date. I had a bad Northern Fowl Mite infestation awhile back, and bought some. Ivermectin can work for external and internal worms too *if* your worm population hasn't developed resistance. So that is what I am using this season spring/fall.
Next spring/fall I will try the copper sulfate in the water...I think that is for 3 days.
I will then assess if that is adequate to keep worms at bay. If not, I will reassess what I will use next. Remember, it is best to rotate your products.
I do keep permethrin dust sprinkled in the coops, under the bedding at all times. Sometimes I alternate with Sevin as its cheaper (though technically not on label any more for chickens). That keeps a rotation on external parasites.
Remember I live on a small 1/3 acre with about 15 to 18 birds (give or take some) in a mild, wet climate, that often doesn't get a lot of killing cold. My soil can build up quickly with parasites especially since rats are a bane in our region. (We joke we can't kill them all...you just worry them enough to go to the neighbors for awhile to give you a rest).
Those in northern states which get very cold, freezing winters, weeks on end, don't see the parasites those of us in warmer, milder, wetter states do. Ditto with those that have rotated acreage for their birds. If I only kept 6 chickens, I would not see as much build up on my land...but I get chicken happy, and keep more since they have plenty of elbow room, but it does tend to tramp the same grounds over a season.
Anyway, that's my herbal schedule....3 days on 6 to 8 weeks off.
I'll link Molly's Herbals below if you are interested. If you poke around on her site, you'll see more natural and herbal philosophies to read as well.
http://www.fiascofarm.com/herbs/mollysherbals.php/categories/herbal-wormer
LofMc