Pictures of paintings really do not do justice to the paintings, althought we artists try to make the image look as much as the artwork as is possible. The camera 'sees' less than what the human eye does.

Here are some details from "Towards the Light", so you can see some of the strokes that make up the painting.

Water:



Foliage:



Stones:



As you see, the quality and direction of strokes varies as the surface vary, and as is needed. It wouldn't work well to do this kind of water with the same type of random marks as foliage. A boulder wouldn't look rounded by age and water if all strokes had been horizontal.

Initial strokes (no picture), are usually made with the side of the pastel stick. Think of it as a broad brush, and the tip of the  pastel stick as a small brush.

Varied strokes tend to give a livlier appearence to a painting, and helps build character and form.