I love the grid method myself, I also use projectors, overhead projectors for large murals, light boxes...I use dividers, proportional dividers. Although what I have started to do years ago is I do the initial grid drawing on a separate piece of vellum or tracing paper and then transfer to my main support, reason is I had messed up several pieces I laid out right on the main support and had to spend all of that time redrawing the sketch again...I lost a lot of energy from that and some of the pieces I never even finished.