A very dark contrast over a very light primer usually is going to give messy results.
If you're interested in how I did mine...
Blue:
Spray Black (
GW black spray)
Zenithal Spray White Scar
For vehicles, zenithal spray Blue
Wash Dark Tone / Nuln Oil
Heavy coat Asurman Blue Contrast
Drybrush Vallejo Magic Blue then very lightly with Magic Blue + VGC Ice Blue
Red: Mephiston Red
Gold: Retributor Armour
Metals: Leadbelcher
White: Vallejo White Grey 90.993, for large areas base first with 70.986 Deck Tan
It may sound complicated, but all those steps are super fast. Prime black, zenithal spray white or blue only takes a few seconds more than a single coat primer, washes only take a few seconds per model, and the final drybrush is what makes it look a lot cleaner and sharper than just a pure contrast even though it only takes a few seconds per model. I found using the blue spray for the zenithal helped make the end result a bit smoother on vehicles, but on infantry the difference was negligible. You could probably get away without the blue spray if you don't have easy access to blue rattle cans.