Obviously, this shouldn't be done by anyone not trained and experienced in doing it.
The pin punch used to knock out the old rivet must be narrow enough to fit in the drawbar's rivet hole as it drives out the old rivet.
I use a 2 oz ball peen hammer to flatten the rivets, making sure the drawbar remains firmly positioned on the safety side of the file edge so the spring is properly tightened against the drawbar. It also helps to make sure enough of the file is above the vise jaws so the drawbar clears the top of the vise.
The safety edge of the file is just being used as a working surface.