Preformed as in curved?
Is the surface of your countertops laminate?
Although there are diy kits for painting countertops, for optimal success preparation steps and application instructions must be followed strictly.
I would use a kit. I recently bought a Rustoleum kit for my sink and was really impressed. They also make kits for counters.
How ever you paint them I would then cover them with epoxy so it lasts
Buy the rustoleum kit. Its worth it. I used it in my camper trailer and it was awesome.