Reducing Glare in the Paint
When painting larger surfaces, brushstrokes can sometimes be noticeable. There is absolutely nothing wrong with the textures created by a brush, but they can be a burden while you are working on a painting. In some cases, even in the ideal studio lighting, small ridges and peaks in the wet glossy paint can reflect light, making that area of the painting appear lighter in value than it actually is. One way to solve this problem is the make the paint more fluid by adding medium and apply it using a soft brush. However, this approach isn't ideal if you prefer the paint a bit more paste like and stiffer. The best way I learned to control this problem is to make as many of my brushstrokes vertical as possible.
As you can see, these two swatches appear to be a different value, however they are the same. The only difference is the left side is painted with vertical brushstrokes and the right with horizontal. Notice how the left appears texture-less. Paintings completed with mostly vertical brushstrokes and quality sable brushs will have a such a smooth surface, the viewer will be left guessing how you painted it.