A simple search can find you many alternatives to chemical wormers, though few of them will list some specifically for chickens....just general herbs and such that are known antihelmitics. You also won't find dosing recommendations, as there haven't been studies done enough to warrant finding effective doses.
I have a few links on small studies done on pumpkin seeds and ginger in comparison with traditionally used chemical dewormers.
No, I don't use DE, nor do I even recommend it, for various reasons. Some swear by it, though, so they should be able to tell you how they like it and use it.
I agree with you on the vet recommendations....all geared towards making them money but not exactly for the life and health of the dog.
Here's one great link I've found on that topic:
http://thewholedog.org/heartworm.html
And right beside that one I found a study.....
http://link.springer.com/article/10.1007/s00436-015-4416-0?no-access=true
http://connection.ebscohost.com/c/a...xima-pumpkin-seeds-carica-papaya-papaya-seeds
http://www.ncbi.nlm.nih.gov/pubmed/3668217
I usually don't concern myself with deworming much, though if I think about it I'll likely do it once or twice a year to all animals....usually use garlic, ginger root, or pumpkin seeds. If I had chickens in a coop and run situation I might do it more often, but since mine can free range and find their own deworming tools(saw grass is one of these and I've found it in gizzards time and again...the dogs and cats use it too), I don't get too concerned about parasites.....I butcher often and explore the bowels for signs of parasites, finding none, so the birds are being quite efficient at their own worm removal.