Van Gogh’s brushwork seems bold yet careful. I imagine he painted with intense focus and a large, fully-loaded brush.
There’s a clear distinction between colors and shapes. And many of the shapes are outlined with a few sweeping strokes.
His brushwork seems to follow the general contours. This reiterates the sense of form and gives the painting a sense of movement. Notice the ground in particular. So much energy and broken color.
Tip: You can use brushwork and texture to create interest in otherwise bland areas (a clear blue sky, the wall of a building, or in this case, soil and rocks).
Below are some close-ups of the painting which give you a clearer look at his brushwork. The Getty Museum also has a high-resolution version here.