Installing brushes in GIMP on mac OS X
Download a brush set and expand it. You will get a folder with brush files in it.
There are many places where you can put brushes, any of the following should work :
Location 1 :
I didn't put the folders in the brush folder, just the brush files themselves.
To finish, in gimp, in the brushes section, click the reload button at the bottom of the brushes panel.
Location 2 : Anywhere you want!
Go in your home folder (with house icon, you can find it in the "Go" menu and also in the dock by default. This is NOT macintosh HD.)
Go to /Library/Application Support/Gimp.
A new set of folders will appear. One of them is called "brushes" (if there is none, create it). Open it.
Drag and drop your new brush files here.
Just go in preferences, expand the "Folder" subsection in the tree, choose "brushes"
Click on the "blank document" to add the path to your brushes.