Smooth Skin action not working with brush tool

Do not know if touy can turn smoothing off you can turn the trail off.

Stroke smoothing

New in the October 2017 release

Photoshop can now perform intelligent smoothing on your brush strokes. Simply enter a value (0-100) for Smoothing in the Options bar when you're working with one of the following tools: Brush, Pencil, Mixer Brush, or Eraser. A value of 0 is the same as legacy smoothing in earlier versions of Photoshop. Higher values apply increasing amounts of intelligent smoothing to your strokes.

Stroke smoothing works in several modes. Clicking the gear icon () to enable one or more of the following modes:

Pulled String Mode

Paints only when the string is taut. Cursor movements within the smoothing radius leave no mark.

Stroke Catch Up

Allows the paint to continue catching up with your cursor while you've paused the stroke. Disabling this mode stops paint application as soon as the cursor movement stops.

Catch-Up On Stroke End

Completes the stroke from the last paint position to the point where you released the mouse/stylus control.

Adjust For Zoom

Prevents jittery strokes by adjusting smoothing. Decreases smoothing when you zoom in the document; increases smoothing when you zoom out.

Smoothing: Eraser tool

While using stroke smoothing, you may choose to view the brush leash, which connects the current paint location with the present cursor position. Select Preferences > Cursors > Show Brush Leash While Smoothing. You can also specify a color for the brush leash.

Brush Leash preferences