Me personally, I would sand down to bare metal, from that lower crease, down, and about 1-2 inches(minimum you need to remove the cancer), around the wheel wells, adn continue ths trend down the side to the front, on both sides...

Then, use decent rattle can primer, probably 2 coats...

And from there, get yourself about 1 large can of herculiner from pep-boys(approx 60 bucks), and follow the directions from there.. you will have scratch resistance, and rust protection...

I think other brands are available in different colors..but the Herculiner is (IIRC) avail is black only..

HTH
Chase