Silke:

Yes, you can blend Jepe's hair texture maps, and vein maps to use on the Displacement node. The white on black maps work best for this. I have not tried to blend the gray maps with black maps yet.

I have been so delighted with the efectiveness of blenders, I have not used the Math: Add node. It might be worth a try.

LMK

Probably edited for spelling, grammer, punctuation, or typos.