For almost everything, especially ships since I build to pedestal mount, I use full strength colors. If you use the correct colors you'll be fine. The way to tone them down a little is to do exactly what atmosphere does and introduce a little haze. That's a simple process, thin clear acrylic flat 2-3 times more than you normally would and mist it on lightly, repeat as needed. Works every time without arcane formulae, mystic words and holding your left little toe just so on the 3rd rainy Tuesday of the month under a full moon.
Remember, by the time it really makes a difference in the real world the object is going to look white or silver if glossy and dark gray or black if not glossy.
PS- when I bothered most aircraft I entered placed in IPMS and every ship I ever entered did too. Armor placed well at AMPS but since I did things like properly weather desert vehicles with lots of light dust and not the IPMS preferred drag queen style I never placed armor in IPMS.