I like these abstracted tree forms. The best way to paint these is to load up your brush, hold the brush between you index finger and thumb, and drag it across the paper moving your whole arm, not your wrist.
It's also easier to start at the end of a branch and work toward the trunk, pulling TOWARD you.
If you support the brush in a normal fashion, the result is much more controlled, but may look stilted depending on how skilled you are at drawing tree branches. I use fluid acrylics, so the pigment load on the brush is quite loose and liquid.
For more information about this painting, click here to go to my website.