I dip my glass beaded parts in PPG DX520 (may have renamed it SX520) that provides an anti corrosive phosphate coating then a quick dip in water to neutralize the DX, blow the parts off until painting.

For exhaust manifolds I have had mine ceramic coated from a company called "Jet Hot". The have a "cast iron" coating that looks very close to new cast iron and provides a very good look and will look new for years because they will never rust.