I used to used oil trays, they would get to smelling and You would have to dump the oil and clean the pan and refill. I started using a cheap dish washing liquid in some water. If the SHB gets in it, it will kill him also. It is a lots easier to clean too. In the summer I check the level of the water and add some along, evaporation will lower the water level. Several years ago I got SHB pretty good, I did use a ring Fipronil in a DVD case with a teaspoon of butter flavored Crisco in the middle. That and the screens got my numbers down greatly. When I quit seeing many, I quit using the Fipronil. This past summer half my hives I saw none the others you would see 3 to 5.
Good luck with your bees