40k Imperial fists, How to paint yellow, red, gunmetal, OSL

Take a photo of your model before priming to understand were the volumes will be. Prime Model White (any white primer), White scar used as an example. its a good idea to use a low-surface tension primer such as a car primer for this, will help with next step.

Pin shade the recesses of the model, A good idea is to add water to the area you want to pin shade and then dropping in your shade. this will make it run into the recesses easier. use any glazing medium to thin the mix.

Cover the model with Imperial Fists contrast paint or some alternative.

Next, Wash the model with this mix, It is weird to use purple but when thinned and washed it creates a really nice shading effect. I suggest you use Vallejo deep Purple Xpress paint to wash the model, but this mix is as close as you will get. (will update once it gets added)

layer (and/or drybrush) moon yellow, then slowly mix in flash gits yellow to moon yellow to build up highlights, then add pale sand to the flash gitz yellow, just until 75% pale sand the rest flash gitz yellow. follow the volumes of the model.

Make a fine Edge Highlight on the most prominent edges, sharp angles, and brightest volumes. dot with pure pale sand in the sharpest corners.

Basecoat any areas you want red with VMC Black, then add a basecoat on top of the black with evil red.

Continuation of prev step.

Add volumetric highlights starting with Nocturnal red.

Continue volumetric highlights with Nocturnal red and Scarlet red.

push highlights further with only Scarlet red.

Mix Scarlet red and Scarlet blood 50-50 to increase Highlights almost to the max.

Final red Highlights with only pure Scarlet blood.

Basecoat any sections you want a gunmetal with any half dark metal and half Black

layer (and/or) drybrush with a midtone silver+dark silver

Highlight with a very bright silver.

Wash all metal with a brown wash.

Re-drybrush/layer with your midtone.

Mix Striking Scorpion Green and Imperial Fists. this will be the start of the OSL, put into the center of the OSL, such as the Eye-lenses and face grills. (I mainly use a green Vallejo Xpress color Troll Green instead of Striking Scorpion but it will work just as well.)

Mix together the previous colors plus an equal amount of any medium to thin it down. this will be used as a glaze and will be applied to the areas immediately surrounding the light sources.

Thin down the mix further and Glaze this on the areas which would pick up/reflect the light. you can build up these layers as much as you need to.