Rustleom has some stuff for that too, I wouldn't recommend buying any rust remover or anything of that nature unless it's one of the rustoleum car rust remover tiny applicants if not don't bother bc it only makes the job more work and a pain. (trust me)
Just Sand the spot clean and use the exact same factory color from rustoleum. But remember be careful sometimes u can make the rust or spot worse that's why I'm tellin u to use the stuff rustoleum makes for cars
I highly recommend rustoleum I used it to fix up my jeep. I undercoated my jeep with it I fixed the hinges and the paint chips also the bumper it holds up well and you can treat it the same as regular car paint it will hold up and last
Here are some pics of what I did with it....
I had chips on my hood and they got fixed perfectly

any questions let me know I'll be happy to help