Rust and how to protect from it
 

I have a 1990 Targa that I purchased last year and is my weekend driver. When I wash the car I find that the back hatch serves as a watershed and much of it flows downwards towards the back tailight. The area at the bottom really doesn't drain well and i see some aeas of rust. What do you guys recommend?? Can I use rustoleum and just pain over it? This is not an area that would be exposedd once the back hatch is closed so I'm not too concerned about how bad of a job it will look. I'm sure this is a common problem amongst supra owners and how have you guys solved this problem. Thanks