Paint brushes are pretty straightforward; essentially they are brushes with bristles that are used to move paint around. When you are buying a brush, you’re just getting the brush. You will need to purchase paint separately, although on the plus side you have a wide variety of options concerning both paint type and color.Brush pens actually combine paint within the brush, so you won’t need to purchase paint separately. Brush pens are available in a variety of colors and stand out for their ease of use. On the downside, you are limited to whatever paint type and color is in each pen.