I use Tamiya gunmetal and white and I find the gunmetal is fine backed with white. I usually back all metalics with silver but with the shell being for racing I didn't want too many layers so I just backed with white and it came out fine
. When I do the chrome for the windows I tend to spray over the lot and it makes the white pop a tiny bit. I'd deffo back with white or silver before applying the red tho. Being a strong colour it will dull the gunmetal.
