Some ways to naturally worm your chickens is to often feed them pumpkin, zucchini, squash, melon and apple seeds. Also, give them diatomaceous earth as this has been proven to kill parasites and not harm chickens. Some people claim you can't worm chickens naturally but these natural things have always worked with my girls. You can start worming your chickens once the hens have laid their first egg.
I have the diatomaceous earth, I sprinkle/mix a pinch of it in their feed.
I have been using organic apple cider vinegar in their water. My birds are orpingtons. Their butt feathers can be poopy, is that normal?