Why do you use these and why not just silver. Secondly, what is the buff/no buff all about. I assume you could use metalizer on a P51? I have always done silver.
Metalizers can be purchased in different metal shades. The most popular is aluminum, steel, titanium, and exhaust. Metal aircraft skins are made of more than just one metal. Some have three or more metals used on the exterior. With metalizers you can get the different shades, which makes the aircraft look better.
Buffing metalizers can be buffed to produce different shades, depending on how much you buff. Non buffing shades usually have more of a flat finish than the buffing type.