! It's not advisable to paint grills, because of the poisons that can etch out of the paint.
Wire brush if you must, even have it sand blasted, then treat with a good cooking oil, even animal fat that will soak into the pores of the steel, when a gentle heat is applied to it. Protecting it for years to come!
If you can obtain the material used for non stick saucepans would be a good idea, but in saying that once it gets very hot it just may burn off, defeating the whole purpose. So I'd stick with the animal fat, like lard.
Apply when the grill is warm & make sure you treat the whole thing, not just part of it.
Each time you have finished your cooking, clean the grill & the hot plate & recoat the surfaces in lard or animal fat to protect it until next time you want to use it.