Hi. I just bought a BBQ and looked online at tutorials for seasoning. I did what it said and applied oil to the cast iron grates and also the inside of the lid. The grates were a success but the inside of the lid is covered in dark brown staining, I assume from the oil burning (the lid is stainless steel). Can anyone let me know what I have done wrong and give me any tips on cleaning the lid (baking soda and vinegar haven't made any difference)? Thanks