Well, this is a good question with no pat answer. Mothballs do work, but are toxic, and it is hard to great rid of the odor they leave behind. I had put them everywhere inside and in the basement areas after we got mice on a winter camping trip. No single thing seems to work. Traps, sticky boards, sound generators. Fresh Cab seems to work, and no, we have not had the rodents eat them. Cats seem to help, as they seem to encourage the mice to leave after they have entered. We have had them in the ceiling chewing the foam and other areas. The seem to gain access to the basement, travel through the heating duct into the upstairs, or up the back of the refrigerator, into the ceiling. Most Class A MHs have a basement so finding the access points using light is a pretty much a loosing exercise. Using screen to plug holes sounds good, has anyone ever had wiring damage from rodents?
