I have four cats, siamese with attitude. If you've never lived with a siamese or similar breed, you don't know how it is. It's a lot different than being around your local Fluffy, believe me. Their names are Epicenter, Iridium, Hurricane, and Ricochet. Get it?
They will jump on the hood of a warm vehicle in the garage. They get up just fine; it's going down that gets their claws out. The hood is the only really vulnerable place (on my trucks, sorry). An old quilt on the hood does the trick. It looks kinda silly, but only takes a few seconds. A complete body cover works, too. They are about $100. I have one for my Ranger and my Acura. They are extremely light with a very soft interior. It's a hassle to use, though, so it takes a little discipline.
Cats are very tenacious animals. My dog, Moses, is much easier to control. If I didn't let my cats out there would be hell to pay. I know a human is responsible. I do not deny that and I accept responsibility, but humans aren't 100% in charge of a cat and you have to factor that in. Fortunately, they sleep 20 hours a day. If you do want to use a spray bottle, approach slowly. If you rush a cat they will freak out trying to get away (You'll never catch Ricochet. No one has EVER caught Ricochet!) , and that's when damage can happen. You don't want them 'treading water' on your paint.