What Product To Brush On Rusty Metal, Suggestions Please

I have used a product called EvapoRust with great success. It works amazingly well and is billed as "nontoxic". It is available at major auto parts stores, including O'Reilly.

That said, I used it to treat the insides of a small motorcycle gas tank, where the metal was immersed in the chemical for several hours. Not sure how it would work as a "brush on" treatment. But I suppose you could immerse your step in a pan or something.