Hello Morgan,
Those are good questions you have. I am in the process of "de-worming" my flock now. I do it twice a year. I de-worm in the late winter, usually the last half of February when we start getting warm weather and before my breeding season begins in early March. Then I de-worm in November before the start of cold weather. I use a liquid solution which is actually for domestic poultry and swine. It's name is "Wazine 17." It's active ingredient piperizene is for nodular worms and round worms. You can get it from any feed store it comes under a number of names. Of the type I use I use about a tablespoon per gallon of water I then distribute it to the pens and let the birds drink from it for 24 hours. You need to repeat the process again in 10 days so that way you kill the worms that hatched out after the first treatment. The de-wormer does not kill eggs that were present during the first dose. Be careful not to overdose as you can kill your birds!