The large sticky traps for rats are already scented, or some are.
It'll catch anything short of very large rat.
Clean up all the pellets and any urine.
Use the spray foam. Two kinds one for large epansion and one for smaller expansion. It's kinda cold now but somewith strong light inside and you underneath will find most of them. Be sure to chek you water compartment under shower. Dealer left huge holes big enough for cats. Factory fixed it and foamed it.
It will take as long as it takes.
Traps are not as sensitive as I remember from ancient times:) cycle the trip a few times first. Even a little peanut oil on the trip. They may not be getting caught because the trap smells of you or something. Rinse it under hot water and let it dry for a long time. That should get rid of human scent but not gas or something.