When I etch my wagon wheel wrought iron, I polish the metal yo 400 grit, then etch in warm white vinger.you we'll need to take it out wash it off to see how much grain showing, then I use a green scotch bright pad . The I get some gun metal blue and blue it . The buff it with with green pad. Next I heat with a propan torch tell hot and spray with wd40. Yes it will flame up on you.let cool a rubb it with a clean rag, for me I fill the holes with job weld potty , that away the hole does not get bigger, ask me how I know about that.