So apparently I'm not as well read on chickens as I thought I was... Had no idea I was supposed to be worming them! Luckily I had a friend tell me about Ivermectin (works on horses, cows & goats too!). It comes in pour-on, injectable & paste. I read online that you should only use a pea-sized amount for chickens.
Took me awhile, but I was able to catch one chicken at a time and feed them a small piece of bread with the paste on it. The only downside is that you have to discard their eggs for 7 days following the medicine. You can also use the pour-on ivermectin to treat mites. Just put a few drops behind their neck (just like you would with cat or dog flea drops). Sounds a lot easier than dusting them with diatomaceous earth!