Until there's better scans for the
WD paint chart/poster thingy- I suggest going from this set of images.
TLDR:
For the red, Base Mephiston Red--> Wash Carroburg Crimson --> Layer Evil Suns Scarlet --> Layer Wild Rider Red. For the black, Base Cha- Abbadon Black

--> Wash Nuln Oil (Truly, it is the god of washes) --> Layer Dark Reaper --> Layer Thunderhawk.