These brushes are the result of hours of experimentation in which I created a set of brushes with smudgy, life-like, soft textures that look so real that it's hard to believe that they're vectors.
The trick when using them is to make sure you set the opacity to 'Multiply'. This makes the lighter colored edges blend seamlessly with the background. Layering the brush strokes creates beautiful color variations and tones as seen in the preview images.
https://creativemarket.com/TheArtifexForge/505394-Charcoal-Brushes