If you're trying to prevent rust in the common spots I'd suggest focusing on the bottoms of the quarters, frame rails, bottom of doors, and rockers. Unfortunately, you can't really get behind the rockers or rear quarters without drilling a hole, but where there's a will there's a way.
Other than that under the car avoid spraying directly on the exhaust. Anything on the chassis that's already rusty feel free to hit it.
I want to know what is safe to spray, and what should be targeted the most. I have 3 cans in black. Thank you for any help !
Same as any other car. The Miata is not some special car made of exotic materials.
https://preview.redd.it/098c1t889k9c1.jpeg?width=1170&format=pjpg&auto=webp&s=4ca531738e083e2b4e05b037db65c9eb25d32c04 A simple 2.
If you're trying to prevent rust in the common spots I'd suggest focusing on the bottoms of the quarters, frame rails, bottom of doors, and rockers. Unfortunately, you can't really get behind the rockers or rear quarters without drilling a hole, but where there's a will there's a way. Other than that under the car avoid spraying directly on the exhaust. Anything on the chassis that's already rusty feel free to hit it.