- Select the brush, hit Ctrl-C, and Paste using Ctrl-V
- Select the brush, hold Alt and move the brush, leaving a copy in place of it's origin.
- Select the brush, hit Ctrl-P, which will make a builder brush for it.
If you use the 2 above, you HAVE to rebuild your gemomitry before advancing. Also, note that building geomitry alone wastes pretty much of your RAM memory usage. This might tend me, possibly you as well, to use the Ctrl-P (or just rightclick on your brush, select polygons --> To brush) as you dont constantly have to rebuild and waste RAM.