Mouse Protection while in storage

What is the a common discussion here on keeping mice out of a stored vehicle. I use moth balls/flakes in my pontoon boat,since it is open air so the aroma is not so bad in the summer while cruising. That wont work in a closed car,,,,, so here we go,,,Irish Spring soap, dryer sheets, homemade recipes have as many failures as successes. Mice eat the soap and dryer sheets. I got some Granndpa Gus bags and spray, but some say that does not work either. My Swinger will be in a non-heated shed with two boats,, we sprinkle mouse poison around the inside edge of shed. I had a fellow tell me today, to leave the hood and trunk open, and put tape over the air cleaner openings,,,, meece like more privacy so they stay away from engine and trunk if open,,,, but, can't use my car cover then. The Gus bags, since the work with aroma,, should work in the cabin of car,,,,,,should,,,,,,