Have you used what they call tanglefoot it's a deterrent for bird roosting . it's come in a tube like caulk and it's clear and is very sticky. just run a bead at the corner or smear some around the roosting area.
I see that stuff everywhere full of pigeon feathers, droppings and in general looking like a black mess. While its used for birds I would never recommend that for bats, if it is viscous enough it's likely going to act as a huge bat trap or at the least end up on them where as mammals they will groom it off or try to and either die due to ingestion or due to trying to fly with the weight of all that product fooled up on them.
I've had this same question multiple times and have never seen a pro suggest this.
Please don't use "tanglefoot" or anything like it, stick to the slick sides ideas which arent meant to kill bats but actually deter them.