Long time ago we used mothballs in our packs when above timberline, while leaving them behind for day hikes to higher places. Mainly for marmots. It was nasty, unpleasant stuff. Not sure it worked as advertised since we didn't have any problems. Gave up doing that a long time ago as well - we were certainly being deterred!. At the places we were then, I'm not sure the vermin population knew what was available anyway. They certainly were not human tolerant and except for the very curious would not even show themselves while we were around.
This was well before canisters and a good tree hang was successful.
ALL of the damage to our gear and food has been from mouths that can't be more than a 1/4" across .. mice and rodents chewing through zippered pockets. Especially when you plop the bag overnight ON TOP of an active access hole. DINNER BELL!!
No bear is going to invest any energy or time on a car that doesn't look or smell of a reward. If you watch films of how a bear traverses a parking lot, they spend no more than a couple seconds looking in a side window then move on to the next presentation on the buffet line. Very much like the kids that would go down the line of pay phones checking for loose change. They are not going to break into a payphone unless it is really worth their while. But they will continue to check because they (or somebody) were successful before. Not sure those composting fries in the folds of your seat would be sniffed out from outside the window of modern cars.
If they are, its probably not a healthy environment in there for humans anyway.

You just get a different detailing job than what you are used to.
Bears (and raccoons) certainly don't know that a soft drink can, left on the floor, is empty or a 0 calorie diet. It simply looks like it should be something good. Same with paper ... umm was that a food wrapper? Large brown paper bags are grocery bags. How are they going to know it is full of dirty clothes until they look inside? Back packs and sleeping bags mean food especially if they are covered up with a nice picnic blanket to keep humans from seeing and stealing them. Doesn't stop humans. Doesn't stop bears.
If you put smelly stuff around the place, its not going to take long for a light bulb to come on that indicates humans are surely hiding stuff there or they wouldn't advertise it.
If you are mothballing your car, please park it way over >>>>> there.