Most of my hives have an aluminum casserole pan with edges rolled for strength, with 1/2 to 3/4 inch of used cooking oil in them. I have a back door to service the pan of oil, I pour the oil through a $1 plastic strainer I got at the $ store into a 5 gallon bucket and reuse the oil. The bees seldom know I am there when I service the oil pan. No mess, no SHB, if I stay on top of servicing the pans. I have used pollen sub on the oil and/or a spoon full of "slimeout juice" IN A FOIL CUP on the oil as bait, seems to work quicker on an infestation of SHB. My DSBB have 2 3/4" space for the oil pan with #8 hardware cloth for screens.