I use the pure peppermint oil. I place 3-4 cotton balls in a small container and place them around the MH. I put 2 in the bedroom, 2 in the bathroom, 1 in the toilet room, 2 in the kitchen, 1 under the dinette, 1 behind the passenger seat and 1 by the brake pedal.
I will put moth balls in a plastic container with holes in the lids and place them by each wheel, one in each cargo door, by the batteries and 1 by the motor. I cannot smell them in the camper.
I keep the camper plugged in all winter so I have 2 ultra-sonic devices in the coach, 1 in the back and 1 in the front. I also place one underneath the MH facing up so the ultra-sonic waves can bounce off the bottom of the MH.
When I winterize I will take everything out of the coach and give a good cleaning. I vacuum all the cabinets, carpet, etc. I also wipe out the cabinets with a household cleaner.
During the season the only things we remove is the dirty laundry and the dry food that could attract mice. The dog food, bread, chips, etc. I leave the MH plugged in all the time so I can run the fridge to keep beverages cold, we like to be able to leave as quickly as possible so we have it down to loading clothes and food.
I have done this the last 3 seasons with no signs of mice, the first 2 seasons was in our travel trailer and this year the MH.