Same advice as above. Use a foundation color between the red and black.
The color you choose will effect the red outcome. Medium brown (like flat earth or beast fur colors) will make a richer, deeper red. Bone, off white, light grey, will make a brighter red with more "pop", but
I've found that the red paints sometimes need more than one coat over the lighter tones as well.
The same trick works well for metallic trim over black; browns for gold and greys for silver.