way to buff out barracuda trunk plate?

Actually, the 1969 Barracuda has a textured silver finish. You can get spray cans of this paint from Eastwood. Although the texture may not be 100% perfect, it will look more accurate. The 68 barracuda silver they use on the tail trim is not textured.

As for the areas that are not painted, they are anodized thus not able to be "buffed" like bare metal can be. The cloudiness comes from the age. There are those out there that can restore that trunk trim, but the pricing is outragous.