Many people can't afford to take poop samples to the vet. I just assume they probably have some worms that can escalate out of control. Twice a year my 25 silkies get a .025 dose of Eprinex squirted between their shoulder blades. Other times I use Fenbendazol (Safe Guard) for dogs. Same dose per pound as a dog mixed with food, usually oatmeal and water, letting each chicken have so many bites before passing it on to the next chicken. Both products are available at Tractor Supply. Just my 2 cents.
Yes. Valbazen liquid cattle/sheep wormer or safeguard liquid goat wormer can be given orally. Use a syringe without a needle to administer one wormer or the other. Dosage is orally undiluted 1/2cc for standard size birds, 1/4cc for smaller birds. Redose again in 10 days (either wormer.) There's a 14 day withdrawal period after the last dosing. Either wormer should be at your feed store, if not, Jefferslivestock.com carries both.