You can apply brush strokes to a line created with any drawing tool, including the Pen tool, Pencil tool, or basic shape tools.
Do one of the following: Select the line, and then select a brush in a brush library, the Brushes panel, or the Control panel.
Drag a brush onto the line. If the line already has brush strokes applied to it, then the new brush replaces the old brush.
When replacing brush strokes with a different
brush, Alt‑click (Windows) or Option-click (Mac OS) the
new brush to preserve brush-stroke options previously applied to
the line.