Hi!!
In the Terrain Script, can i add new brushes? how make i it?
Thank you for your comments!!
Create a png file with transparency and save it with the name brush_x.png (replace xxx with a number).
Copy the png into a folder with the name “Gizmos” below the Assets folder of your project.
Restart Unity.
Don’t work… 
It should, I tried it.
There’s a free asset in the store. Maybe you can try this and see how (or if) it works.
Thank you very much!!!
Happy new year!