I strongly disagree with the so-called "pre-shading" tehnique that sadly has gained such a widespread use. It is not realistic and counter-intuitive. In real life the paint degrades from the outside (weather, sun, scratches and chipping, and so on) not from the inside as this "pre-shading" would lead you to believe.
I begin with the base coat of paint as accurate as possible and on top of that various filters and washes are applied.
My base wash is done from grey pigment, dissolved in water, on top of which other filters are applied. For filters the acrylic Vallejo ranges are used, both Model Color and Vallejo Air.
Vietnam SEA camouflage colors:
1. Medium green - Vallejo Model Air 71092 base. Filters: 90% 71092 +10% White , 60% 71092 + 40% 71016
2.Dark green - Vallejo Model Air 71016 base. Filters: 90% 71016 + 10% yellow ,80% 71016 + 20% 71092
3.Tan - Vallejo Model Color 70874 base. Filters: 80% 70874+ 10% white+10% yellow ,50% 70874 + 50% 70872
4.Grey - Vallejo Model Color 70883 base. Filters: 90% 70883+10% white ,60% 70883 + 40% 70836