what is the bestway and what is the best thing to use???

The main (center) part of the grille looks to be bright anodized aluminum. If so, and it is dull, you might try to renew it with a detailing solution especially recommended for anodized aluminum - just don't use anything abrasive, or you can remove the anodizing.

The very BEST way to restore it is to re-anodize it, which is not cheap - maybe $700 - $900? I had a slightly dented/abraded tail panel straightened and re-anodized for $850 by Alltrim in 2009, and it looks factory new or better with the dent totally gone. Alltrim appears to have stopped doing new work, but you can still peruse his web site, http://www.alltrim.com/index.html. Use the Google search button at top right of most Moparts pages for recommendations on re-anodizers. Or call Alltrim and see what he recommends.

Look carefully to be sure whether other different materials are used in the grille, which is common. The parts around the perimeter of your grille could be made of pot metal, stainless, or more anodized aluminum.

I tried redoing mine a few years back. I couldn't get it as nice as I would have liked. Talk to Marcos at Anobrite. I think its Anobrite.com? That's where I had mine redone. They aren't cheap but the finished product is beautiful. I got good results from traditional aluminum polishes. Several people I know have purchased the anodizing stripper from Eastwoods. They stripped off all of the anodizing and run the grills polished instead. If your not trying to do something 1965 correct this is the route I would go. Have fun repainting all of the black detailing in the headlight bezels...