Polishing the metal parts works great. Use some fine steel wool or the brush wheel on a dremel (be careful here though as you can soften some detail). Once brightened with the wool, you can burnish the metal with a toothpick or bamboo skewer. This gives a nice finish. I use a black oil wash to make the undersides of lames, armor pieces etc stand out and then do a final coat of tamiya smoke. This further takes care of some illustrative shading and seals the metal so it won't oxidize. Gives it some nice depth too.
In the case of a figure like the roman or some of the medieval stuff. you can either mask off the fabric/skin/non metal areas and use a spray primer or just thin out your primer and brush it on the areas that will be painted.
Mike
"Imagination is the dye that colors our lives"
Marcus Aurellius
A good friend will come and bail you out of jail...but, a true friend will be sitting next to you saying, "Damn...that was fun!"