My thumb is the best SHB trap yet. If I see a beetle in one of my hives I kill it with my thumb. If you have hundreds, set up an empty brood box on a bottom board next to your hive, move the frames over one at a time, killing beetles as you go, kill all of the beetles left in the old box, then move the frames back one at a time, killing more beetles, then kill all of the beetles left in the extra box. It also helps to have a person designated as the beetle killer and a frame mover. It seems drastic, but instantly ridding your hive of a few hundred beetles frees up the bees to do more productive stuff.
With 20 hives I don't have that much time. Beetles hate light. As I inspect they move down in the hive and into the pans.