This look is usually created with a filter or plugin rather than painted manually with a brush set.

Based on the community answers, likely options include:

• Fractalius: often used for glowing, flowing line effects.
• Topaz Clean: can produce a similar painterly/curved texture globally across the image.
• G’MIC filters such as Rodilius, painting, or Whirl drawing can also create related stylized results.

One suggested workflow with Topaz Clean was:

1. Apply a stylizing preset such as Curly Smooth.
2. Duplicate the layer.
3. Apply a Gaussian blur.
4. Set the blurred layer to Screen blend mode to add glow and softness.

So the effect is generally semi-automatic: a plugin/filter generates the base texture, and then you refine it with layer blending, blur, masking, or opacity adjustments. Brushes may be used afterward for touch-up, but they’re usually not the main source of the effect.