We have used dryer sheets in our TT for the past 9 years and have never had a mouse or or other critter problem. We also use Irish Spring soap bars, cut in half or thirds. We place the dryer sheets at all openings and where pipes come in to the trailer, all the corners, the outside storage area, outside shower, hotg water heater, and the cabinets. The soap pieces go pretty much in the same general inside ares. Probably a little bit of overkill.
Don and Laura + Critters, Eloise and Cooper