My theory on protecting your car and stuff:
(Gleaned from living in the rurals, Brooklyn, Chile and other places)
1. It helps to have a crappy car. Not worth stealing for parts, resale etc. (Still vulnerable if stolen to be used in another crime). No hub caps. Unwashed is also a plus.
2. Nothing valuable showing. Radio, cell phone charger cord, etc (and CDs mean CD player somewhere)
3. Always bring some clean trash like old sun bleached newspaper, empty MacDonald bags etc. When leaving car spread on dashboard and rear window shelf and some on seats etc. This gives the impression that you are a slob and the car is trashed. (Guys in NYC used to spray paint their valuable bikes with all different colors and lock them up. No one can sell a messy bike).
4. Sorry ladies but hide anything that says you are a woman. No bumper stickers about the goddess, etc. Get a big pair of worn work boots from your brother, male friend, dad etc. and leave them in view. Vandals tend to be young loser males who are cowards and like to think the target is weak i.e in their mind a "chick".
5. Park in a puddle or in a muddy spot. Real pros often will not steal a car in a puddle to not get their shoes wet. Vandals are also looking for an easy target.
Note: Spent ammo is double edge sword. Maybe a shotgun is locked in the trunk. No fool carries a long arm backpacking. Maybe some spent 45 cases, but they usually would end up on the ground or saved in a bag for reload. Out of state plates? Did you really bring your hand gun from Canada or Mass.? So anyone with the slightest of gun sense would know it’s a bogus scare tactic.
I have seen people leave gasoline bottles on the tire of the car, to avoid the fumes inside. Bad idea. Vandals with a liter of gas??? Better to cache your bottle in an odd spot off the parking lot that is easy for you to find.
Just my 2 cents