When working with Paintbrush Tool and Eraser Tool in GIMP, you can use different brush types according your need. For instance, if you want to create a cloud shape, you need a cloud-shaped brush. Unfortunately, GIMP comes with a limited enough brush collections. The good news is, you can install Photoshop brushes in GIMP.
GIMP has a good enough compatibility with Photoshop. First you can open PSD files with it, and second, you can install the Photoshop brushes as well. A set of Photoshop brushes itself is available in an .ABR file and GIMP is capable or reading that format although the original file format for brush in GIMP is .VBR
Installing a set of Photoshop brushes in GIMP is extremely easy. You just need to copy the .ABR files you have to the “brushes” folder in the GIMP installation folder. The location of “brushes” folder can be different depending on the operating system you use.
In the vast majority of Linux distros, you can find the “brushes” folder with the structure like this “/usr/share/gimp/*GIMP version*/brushes/”.
While in Windows, you can find the GIMP installation folder under (usually) the “Program Files” folder in drive C:. Then you can go to “share\gimp\*GIMP version*\brushes” to copy the .ABR file.
An .ABR file can contains multiple brushes, but usually in the same type. For instance, this .ABR file contains 24 different cloud shapes. You need to restart your GIMP after copying an .ABR file