I downloaded a program called MediBang Paint Pro when it was recently recommended to me. It's a completely free, lightweight program that has many of the capabilities of programs like Photoshop and Manga Studio. Good for artists that need a great program to work in but are strapped for cash!It works well, aside from one detail - it IS a very lightweight program, and it runs pretty slow when your file size gets too big. Other than that, there is no reason not to check out this program. It has tons of cool features like free cloud storage, compatibility with multiple devices so you can work on the go, and direct uploading to the internet. The brushes, while limited, all work perfectly, and there is a way to add or create new brushes.
You can find it here on Deviantart MediBangPaint
! And you can download it here: medibangpaint.com/en/
Also if you're interested, check out the webcomic I'm working on in the video: bit.ly/cybwb32