I had it in my notes but forgot to mention Stan Klimek's masking discussion in Arentz, 2nd edition, p. 215. He describes the advantage of overcutting the corners and also has instructions for using Rubylith D3R as the masking material.
"Arentz," of course, refers to Arentz, Dick, 2005, Platinum & Palladium Printing, 2nd edition: Elsevier/Focal Press.
Wayne Lambert