A word of caution, many people believe their wormer isn't working because some or all of their cattle look wormy. Unless you do a proper fecal (ie under a microscope), you don't know for sure. The wormy look could be due to genetics, minerals/nutrition, or time of year. Other things to consider would be proper dosing or missing cattle. Management methods such as pasture rotation is helpful also. Having your vet do an occasional fecal and helping determine a proper deworming program could be well worth the few dollars spent on a fecal. Also, deworm the calves at the same time. Studies have shown a 29 lb. weaning wt. increase.
I have had luck with fly tags. I put them on in late spring or early summer at the same time I use pour-on. The pour-on kills the flies present and tags prevent or slow down repopulation. Follow directions concerning when to remove. I f you leave them in too long, the low level of insecticide will only help select for resistance. Remember to rotate between classes.