My first attempt of using eraser instead of a brush. For this technique you draw a basic shape and then use eraser to give it detail.
The tree has 4 layers - first I drew a blob of the middle green shade. Then set the eraser to vary in size based on stylus pressure from 1pt to 3pt and kind of deleted parts where branches would be seen. It was pretty ugly. Then with a blob brush I drew the trunk and the branches, made it azure with the eraser, put that layer under the green. Was still ugly. Drew a dark green shape, placed it between the two, made it azure with the eraser. Finally drew the light green with a blob brush on top of everything and used the eraser again.
The ground was done the same way (2 layers - azure dark on top, lighter solid shape behind). The grass was drawn with a brush with same settings as the eraser. Gradiented the background, added mountains, added the frame and the 'stars'.
The fun of this technique is you draw very generally and liberally and in very broad terms. And then with the eraser just make it azure. It's rather simple and easy to do. What's neat is the same can be achieved with a brush - just then you have to be good at giving it a general shape. This way instead of growing your drawing you take away from it - it's subtractive. But because you have layers and isolation mode it's super-easy compared to say subtractive sculpturing.
The stars being on top of the frame but behind the tree give the graphic some depth.