Generally go brighter, assuming that by 'brighter' you mean a lighter shade of silver, for the fabric covered areas as it provides contrast and simulates the difference between the doped fabric and lacquered/enameled/polished metal areas.
This Fury pic is a classic example:
Coloured dopes are generally glossy to start with, but dull fairly quickly without maintenance, they
would relatively quickly go flat and fade due to weathering in WWI, particularly from ultraviolet effects.
Aluminized dopes are not as glossy due to the high content of aluminum powder acting as a flatting
agent.
So with spray paint, brighter and satin for the fabric, glossy for the metal bits.
Jon