help. Shaderforge Normal dir and normal maps

I am trying to make a moss/snow type shader. this is the W.I.P

My problem is I don't know how i can add a normal map to the moss.
The moss is y projected/blended onto the model using This technique

The moss y projection is blended onto the rock using the rock normal-map, this means i cant change the rock normal map without editing the the moss blending (which often leads to a broken shader).
My only idea is rendering 2 normal maps on the same model (Moss Nmap overlayed on rock Nmap) however i don't want to do that because i don't know how and it would be expensive.
Any ideas on how i can add A normal map to the moss?

(Prize - a free moss projection shader when it is finished)

 

From afar, the moss is fine, but up-close reliefe mapping is essential.
Perhaps someone knows how i can achieve the same y projection blending with a specified normal-map input? or maybe by height-map?

 

I think you are looking for this: