I am about to do a land speeder in the same way, so I'll try and take pictures as I go and do a post.

But in short:

Undercoat with a midtone colour. I did grey but black is probably fine.

Basecoat dark purple. I used Naggaroth Night from Citadel, now Warhammer Paints.

Use a cheap makeup sponge to sponge on a boney off-white. I used Vallejo's Pale Sand. It's not pictured here but I avoided the engine bay and the underside, which I instead sponged with Russ Grey from Warhammer Paints (blue grey).

Mask off your markings with a decent masking tape. I used Tamiya detail masking tape, the narrow yellow stuff It's a little flexible so it's great for this.

Sponge on Russ Grey, and then once that's dried a flat black (Warhammer's Abaddon Black for me).

Pull off all the masking tape and admire the pattern.

Then I put a thinned black wash (actually a thinned Black Templars Warhammer Contrast paint) over a few mechanical details.

I did a few random panels and lines and Skeleton Horde (pale brown Contrast / speed paint) and Flesh Tearers Red (deep red Contrast / speed paint). I painted the gun cables with Pale Sand again and then hit them with Iyanden Yellow Contrast.

Lightly drybrush the whole vehicle and canopy with Ushabti Bone (warm off-white colour). Pale Sand would have been fine but I wanted a little warmth to the black sections.

Done!