Here are one method for using brushes in figurative oil painting
Traditionally is used three main types of brushes.
One to dose the paint on to the surface, one to distribute the paint over the surface and one to blur brush strokes.
You can use a range of different brushes for each of the three functions.
Often painters choose not to use all three functions in their paintings.
Add the paint to the canvas with any suitable brush
Distribute the paint with a sable brush
Use a large sable brush for blending
Finally use a Badger blender to unify the surface
The finished painting is in this example is pretty blurred but it is up to you what finish you want.