hi
i created an terrain and some low poly tree models of 10 kinds,i want arrange the tree models all over the terrain,terrain is so big,i cannot manually position the trees upon the terrain,so i need to create a custom brush ,with it is paint the my tree models all over the terrain,but i don't how to create a custom brush,i googles for info about creating a custom mesh brush,but no use so far.

plz help me out in this