Warren in Lancaster, PA
Roubo did not bore out the waste, did not use a pilot hole, and did not use the V method.

Roubo used a fixed pin mortising gauge, so a different gauge for each chisel, which is most accurate. He started the mortise at the near end with the bevel away and chopped straight down. Then he gradually moved the chisel toward the far end riding the bevel. Then he turned the chisel around and gradually moved toward the near end, still riding the bevel. He occasionally used some sort of grease to lubricate the chisel.

This is just about the method Daniel O'Hagan taught me in 1978. He called it the "California Method"

Here is an engraving of Roubo's chisel and a fellow mortising. Note upright relaxed posture, short handled mallet, left hand on the chisel handle, left arm rather extended.