I heard somewhere that if you are going to spray the louvres spray from a distance to get the right texture. Normally you'd want a wet coating on the surface. To get near the original texture, you don't want the wet look. By spraying farther from the surface, it has time to dry a bit and not flow.
Probably best to practice on something else and on the bottom of the louvre before doing the top. Too far and it won't adhere, too close and it will flood, too close and it will coat to heavily.
As far as removing the whiting/fading/oxidising/etc ... I had moderate luck with Back to Black but I have really good luck with a hydrocarbon based SS spray cleaner applied to the louvres first and followed with B2B. The cleaner removes the white. The B2B enhances and protects it.
YMMV but it is worth experimenting first (just don't use any silicone based products as they mess with paint adhesion)