Ditto on using those 'fabric dryer sheets'. Buy the cheapest generic type you can find, not the name brands. I think the vermin hate those genric the most !
Been using these for winter storage of both boat and my convertible car.
Lay them all over any openings on interior. I also place dryer sheets in different places on the engine, especially near any wiring.
So far no problems or signs of vermin anywhere ! Knock on wood !
BD