whats the best way to clean a cast alum valve cover?

whats the best way to clean a cast alum valve cover?....and once clean and polished can it be cleared?

hydrofloric acid, its almost the same as pool acid from home depot

thanks...and i love your yota..its modavation to finish mine...as you see in the pics with the wire wheels it only gets about half of it

yes you can clear it after polishing