hi, i just finished the skiff russian 122mm spg. i “preshaded” the model with my airbrush…so my only question is do i still add a wash or is that basically what the preshading accomplishes? the model is painted in iraqi sand. thanks people 
I’d say you still need to wash. It’s a totally different effect, but I’ll let the weathering experts give you the final answer.
While pre-shading will give shade variations in the vehicle’s image for an enhanced “3d effect”, a wash is used to bring our the small details like panel lines, weld seams, depressions and creases. By adding a wash and defining the detail lines of the vehicles surfaces, it breaks the solid image of surfaces into details, thus giving it more life.
Also in some cases, a dry-brushed effect is necessary to add further to the 3D effect by highlighting the raised portions of the vehicle surfaces.
I agree.
Add the wash. It will add some more depth to the model.