Oils are used to accentuate the panel lines and make them visible. At some point, I use oils (oil paints) for painting the craft. The chalk powder is used to dust the aircraft a bit. Since it's a carrier based aircraft, ground dust is minimal, but a bit more on the soot comming from the gun barrels.
It's a beauty! The quick glance made me think I was staring at a real plane on the run way, just photoshop away the runway. Damn, I am enthralled by your skills. Puts my simple style to shame on the mecha models. Excellent job!