Specular map for landscapes help



I am doing some landscapes creation with World Machine and then I import that into 3ds max, I use the maps in 3ds max.
I have some problems with specular maps for landscapes. Does anyone know any good tutorial on that particular topic. What should the specular map for landscapes be like? What should I pay attention to?
And could somebody explain flow map to me? As I understand it, It gives some flow details to the model. But where should i put it in 3ds Max? Which slot? Should I make composite map with some other map?

Sorry for begginer questions and thank you for sharing your knowledge.