Who uses preshade? And is it for light colour vehicles? Can this effect be achived without pre-shading?

I've used pre-shading on aircraft including the F-18 I did. Its color was light grey so I pre-shaded in black to get the effect. I've also seen post-shading (not sure that is the correct term) used on darker vehicles. The dark base coat is applied first and then the lighter shade is applied in the center of panels, doors, hoods, etc. Hope this helps.

Yeah i usually use post shading for all my vehicles, as i use a black/very dark brown wash/Filter over that so it comes out not to dark or light, plus i think it gives a better sun-bleached effect, where as painting black and then going over it with your colour, your always thinking have i put to much or too little paint over the shading. Pre shading works better for aircraft than armour, and post is better for AFVs IMO.