Gridding off a profile quite often requires the input of a scenic artist. Most often the carpenters will lay out plywood, grid it off into one-foot squares, and then request that the scenic artist or designer mark the profile. Depending on the personalities involved, you might wind up marking the outlines inside the squares and then just getting them checked by a more artistic member of the team. (Unless, of course, YOU are that person.)
Once the outline of the piece has been marked in charcoal, it is a good practice to retrace it with a Sharpie marker so that the line is clearer. Charcoal tends to vibrate off the plywood during the cutting process, and having a clear and indelible mark makes the job of cutting much easier. The more complicated the work is, the more important it is to retrace. One word of caution: laquer-based pens can be difficult to paint over. This is especially true if the paint is a light color.