GIMP is an open-source image editing program that allow you can use Photoshop brushes in GIMP has a large library of free brushes that can be downloaded, Here are a few high-Resolution Free GIMP brushes which will speed up your project and make life easier to be working on. Most brushes have been converted from photoshop so dont worry if they say photoshop in the image. Please read the terms before using it.
To install, unzip files into the brushes folder in your GIMP program files (usually C:\Program Files\GIMP-2.0\share\gimp\2.0\brushes in Windows or /home/username/GIMP-2.0/share/gimp/2.0/brushes in Linux) and then restart GIMP.
Here is video from youtube: How to Install brushes on Gimp 2.8
Guess you may be interested in the blow excellent related articles as well:
Smoke Scene Design
This is a tutorial for installing Photoshop (ABR brush files) Brushes onto the GIMP!!