The brushes shown above are the two brushes I use. The first (soft round) for all sketching and most of the painting. The second (spatter) is just occasionally to apply texture. You must be careful when using textured brushes as they can cause a repeating pattern (although adding a ‘scattering’ setting can help) so I try to use sparingly and vary opacity. Note that I have ‘Transfer’ enabled and the Opacity control (in that tab) set to pen pressure. This means if I press harder with my tablet pen, the darker (or less opaque) the painting will be. This gives a very natural feel to drawing and painting.