The technique I already knew from my childhood from my father and was already impressed by the pen. I use it for writing and correcting with an HB lead and drawing with 2B and 4B mines.
Only a sharpener should be ordered to do so. This is usually integrated in the end cap in many more modern designs, while Faber fort he lacks.
With a bit of tact can sharpen the 2mm mine in a regular Spitzer, or use the small blade of a Victorinox eg so.
My favorite and an absolute All Star in the office, the pencil case and on the desk!