For every production I do I make a document called a "Blocking Key." This document contains the actor's name, the main role s/he plays, or Ensemble etc. I then devise a one or two letter code, sometimes the actor's initials, sometimes the first letter or letters of character name (it depends on the show) and that becomes the actor's designation for the blocking script, and for the calling script, if I am taking visual cues off that actor. For example, I am currently doing a show with the characters "Robert" =Ro, and "Harry"= Ha. In this particular production, all actors have a character designation, but in some shows I use the actors'' real name initials (John Smith=JS.) You can write your chosen designation anywhere in the script you need it, and it always will refer to the same person or character. And, I ask that all my assistants, if any, use the same designations. I've been doing this for years, and it works very well.