I have been feeding DE in feed for years. We get our feed custom made.... we run a cow calf operation, and so get our feed by the ton delivered bulk. The best way to incorporate DE in a small operation is to add to the loose mineral/salt mix... or in a sweet feed. Our custom mix has about 100-150 lbs per TON.... very miniscule in the scheme of things.
Use like a TSP mixed in a 2 qt scoop of feed once or twice a week... or a pinch daily....
The same with our chicken feed...I have some purebred show birds, had a free range laying flock and also, I raise broilers (CCX) that I get from a couple commercial poultry houses when they come and get the birds.... I get the left over "culls" that are usually the small ones..... sometimes get 10, sometimes get 100 or more; about every 8 weeks or so if they leave any behind. Don't do them in the coldest weather because they come out of a climate temp controlled house and cannot take the cold shock.... So I also get a 16% layer feed delivered bulk.... 2 tons at a time..... and feed it to the layers and the ccx. I have the DE added to the feed when it is being made... I feed pellets so they don't waste it like a finer ground mash feed.
The DE actually is "rough enough" in the gut tract that it will puncture the soft bodies of worms/larvae and they will die and be expelled. It also does the same in the manure... as the larvae hatch from the eggs.... It works the same as a dust... and I add it to say ahses that I put in the coops for a dust box... especially in the winter if the birds cannot get out to dust. And I have used it direct on them as a dusting powder instead of a commercial brand if they have lice.
DE is VERY IRRITATING to any soft moist tissue... don't breathe it as it will iritate your nose and throat and eyes if you get in a "cloud" of it. But it does the job without "chemicals" if used properly. Some people feel that it is not good to use. The vet did some fecal samples on some cows that were wormy, fed DE and then did some again. That is the ONLY thing we changed.... fecals came back nearly 100% clean in a month and the cows looked 200% better just by getting them "wormed". Sold me on it. I did it after another small "hobby " farmer swore by it. We were using the same vet, and he mentioned it, so I tried it. Now I wouldn't do without it.