I'm now doing most of the work with a 2mm rod of sterling silver. This much larger wire than my 0.3mm in Pentel lends a smoother gradation.
Easy does it with silverpoint. That is, apply layers lightly with the confidence that darker values are achievable. Heavy handedness leads to dark spots that then need smoothing. Also, it's most important to leave the highlights open as there is no eraser with metalpoint, short of sanding it out.