Alpha legion Tutorial.
Here's how he does it:
1: Prime Black; as little as needed to get full coverage
2: Airbrush Base with a 50/50 mix of Vallejo Gunmetal/chainmail.
3: Airbrush top of model with Vallejo Silver.
4: Airbrush two coats of 75/25 of Tamiya Clear Blue/Clear Green.
5: Airbrush the flat panels Tamiya Clear Blue from the midpoint down; blend so the strongest blue is at the bottom
6: Repeat #5 with Clear Green, from the midpoint up.
7: Using an extremely thinned Vallejo Silver with a hint of Lothern Blue (like 1:15-20; enough to make the paint appear "off"), airbrush the top of the shoulders, pack, and helmet. Less is more here.
8: Using thinned Tamiya Clear Blue, brush over the highlighted armor sections and blend into the non-highlight areas.
9: Take Guilliman Blue glaze, and drag it down the model so it covers the recesses; this is a glaze and shade at once. I break up excessive pools and cover any overly thin areas. DO NOT WET GLAZE UNTIL YOU GET THE PROPER BLUE. This will result in a model that is too dark. Do a single coat, let it dry. Patience is the key.
Pick out your metal bits in the silver of your choice, nuln oil, and highlight. I use a striking motion to gain a weathered effect.
Finally, remember that the Alpha Legion uses non-standard markings. I show individual tactical squads via backpack coloration, specialists via helmet markings, and rank structure via stripes and shoulder coloration.
For the Emperor!