It's not possible Falcon. The Global method applies the Globalenvironment map to the entire texture. Including parts that you don't want to have reflection. Like panel lines. Or dirt. You need the alpha and the model itself to be set correctly. Specular controls the detail in the light bloom and the bloom itself. The model definies the Specular strength or size of the bloom, and the spec.file will determine how much of that is visible based on the white to black in the texture. It's opposite of alpha in that white areas are "light" and black is none specular. Pure white usually results in to high contrast. Pure black is no light dispersion. Which is also wrong for surface areas. However not for intake areas where you don't want highlights.
DaveQ is right though, you.cant really get a good gloss paint look in FSX compared to PBR. However there are some.methods to getting the paint to look pretty good and not look like a colored metal. I can share those if you wish. But a prerequisite is that the model is set to use the inverse of the Diffuse Alpha channel as the reflection generating texture.