Black & White and Greywash could be a bit confusing at times.
Applying tones ranging from white to black ink is called Opaque B&W.
Greywash on the other hand is a technique using tones of pure black and diluted black ink with water solution. Both techniques have their specific looks when healed.
It is best to consult with artist which technique would be most effective as placement and tone of your skin plays a role too.