I have mostly been doing digital art lately. I do some pencil, some pen, watercolor, etc. but have enjoyed digital for years.
For that piece, and most of my pieces the last six months or so, I painted it with a Nintendo 2ds XL, with the program Colors3d. If you already have a 2ds or 3ds you can get the program for about 8 bucks or less. (My son bought me the Nintendo to play games with him).
It is more limited than some of my other programs, only having three brushes (a round bristle brush, a round flat brush, and a round soft brush), undo, eraser, and that is about it! Also, it is a small screen. However, I really enjoy using it because the buttons all work easily and intuitively together. It all fits in a small package and is easy to hold for long periods of time. I can paint with it almost like I would with a portable watercolor pallet. Also, I enjoy that you can upload it to their gallery and people can watch the painting process. This is good for learning techniques because you can watch some talented painters there. Here is the video for that one:
Colors! Live - beach by tall73
Because you cannot crop with Colors3d I find that I tend to do better at making full scenes, rather than just painting something that catches my interest and cropping it to size.
I will sometimes use other programs to adjust the levels and such. And Colors 3d, since it uses the small Nintendo screen, has a fairly low export size. It is vector based, but works like a raster program. So you can export it at larger size than just what you see on the screen. But it maxes out around 1500x1000, which is not great for prints.
Some of my other digital paintings I used a Wacom intuos pen tablet with Corel Photopaint or Corel Painter. I also enjoy vector with Coreldraw. Those programs have more power, but I enjoy just picking up the Nintendo and painting quickly.