Both your actors have listed the best of the best as far as reading that might be helpful in understanding what the actor process is. I might add the Robert Lewis book, Method or Madness and Sonja Moore, who wrote about Stanislavsky in her paperback, The Stanislavsky Method. A later edition, The Stanislavsky System, expanded and modified, was published by Viking Press in 1965.

At best, these are descriptions of a process, variations of a central theme which is to define the tools used by actors all over the world to aid them in reading the map the writer has presented them. A map that describes a physical, intellectual and emotional journey that the character they have been asked to play takes.

To understand that journey in a way that might reflect back on the writer's craft, I think that the reading, while interesting if only to learn and define the vocabulary that describes the process, will not substitute for the attempt to take the journey themselves by actually participating in a scene study class. Why? Read a novel. Read a screen play. Wherein lies the greatest difference? Both describe physical attributes of characters, places, time, atmosphere. Both create an historical reference whether past present or future. But, when necessary, the novel can and often does create thought patterns that bubble with context that is associated with the external form of the story. That is almost always absent in the play and the screenplay. But it cannot be absent in the performance. There is rarely a moment in conscious life that a human being ceases to think completely.

The street is wet, the car aquaplanes, the light turns red. One actress screams and thinks of her children, "Who will feed them." Another actress screams and thinks of her lover, "I'll never see him again!" A third screams and thinks about her face and body, "What will I look like!" Now, not much difference at that moment, the audience sees the peril, hears the scream and then we have the crash. But those different thoughts seen over a 100 minute film could add up to three very different interpretations of a single character. That is what the actor does, and while it is done with the obvious guide of an observant director who is facile enough to suggest adjustments that keep the actor en pointe with script, in the hands of three different and equally skilled performers, the net result to the film could be profound.

The benefit for the writer in experiencing the actor process of building a back story and a mind set would, I think, prove invaluable in developing a character that shows that the writer has not ignored how his characters think and why they think that way. For it is that process of developing sub-text where actors nost clearly define where they have been and indicate the course they have chosen to take in the future.

In a highly collabrative medium, the writer who ignores or does not understand the input reality of all the component share holders does so at her/his peril.