I would recommend priming with Wraithbone or any other light and slightly warm colour. This will make getting a nice tone to the armour easier.
Basecoat armour with Ushabti Bone .
Either zenethal highlight with thinned Screaming Skull from a downward 45 degree angle or glaze in where the light would hit. Since there isn't tones of armour on these boys, you could easily skip this step.
Recess shade with Skeleton Horde thinned with Contrast Medium 1:1. Don't be too neat, the contrast should pull towards the recess and give something like a transition. Now is also a good time to paint the under-suit/tubing by your preferred method.
Recess shade everything again, this time being careful, and using Agrax Earthshade . I used is straight out of the pot, but you could mix in a little contrast if you wanted to make life a little easier. Alternatively, thinned Rhinox Hide works well for this and is easier to control.
Add a chunky highlights of Screaming Skull to all edges and where relevent on panels.
Edge highlight everything again with fine lines of Pallid Wych Flesh .
Selectively edge highlight the most exposed curved edges and corners where highlights meet with a pure white of your choice, like White Scar .
Optional: Battle Damage
Add small patches of Mournfang Brown using dots with a fine brush. Try to stick to edges and corners where damage would occur, mostly towards the front of the Space Marine.
Underline the damage from the last step with fine lines of Pallid Wych Flesh .
White Cloth Sleeves
Basecoat with Corax White .
Wash the cloth with Apothecary White , thinned with an equal amount of Contrast Medium .
Shade recess shade with Thunderhawk Blue or Dark Reaper , depending on the depth of the recesses and definition needed.
Edhe highlight folds with Ulthuan Grey .
Define points and particularly raised edges with a pure white (like White Scar ).
Basecoat with Mechanicus Standard Grey .
Wash with Nuln Oil thinned with the same amount of Lahmian Medium .
Darken deep recesses with very thin Abaddon Black .
Mix Mechanicus Standard Grey 1:1 with Dawnstone and do a round of general highlighting of the cloth. I try and do it in scratchy lines moving the brush in the same direction if possible, to create a little texture.
Add chunky highlights of pure Dawnstone .
Add fine highlights of Administratum Grey .
Mix some pure white into the Administratum Grey and pick out points, folds and prominent areas with selective highlights.
Add final specular dot highlights of pure white (I like Vallejo Dead White ) to points and where lines meet.
Basecaot with Abaddon Black .
Mix Eshin Grey into the Abaddon Black and pick out prominent areas that would catch light.
Add chunky highlights of Eshin Grey .
Add fine highlights of Dawnstone.
Now selectively highlight prominent areas with Administratum Grey .
Mix some pure white into the Administratum Grey and add specular highlights to knuckles, and in the centre of previous highlights on the top of the boot etc.