SafeGuard Liquid Goat Wormer or Equine Paste does a very good job too, and the only worm it doesn't get is tapeworm, which is not too common, and fairly easily seen as small segments that look like rice. It may be found easier than Valbazen, and some people will rotate those two. Be sure to dose your chicken once and repeat in 10 days to kill the worm eggs. Dosage of either is 1/4 ml for bantams, 1/2 ml for regular large fowl, and 3/4-1 ml for very large fowl.
For treating gapeworm or capillaria (hairworm) you would want to use SafeGuard at twice the normal dose for 5 days in a row. Those worms are also unusual.