> and yes JW does not orchestrated his music self.
A film compsoer creates a "sketch" score on many staves (that's lines of music) that includes material for all the parts of the orchestra the composer will be using.
HOWEVER, John Williams creates these "sketch" scores so that they include so much detail that the orchestrator (the one who basically finalizes the score) has very little work left to do. So to say that Williams does not orchestrate his own music is partially false. He simply does not write out the full orchestral score.
The orchestrator's job is to take this "sketch" score and divide up the brass parts, the string parts, the woodwinds, add the phrase markings, as well as any particular instrumental effects asked for by the composer, etc...
A good composer, as is John Williams, does not leave any "composing" work to the orchestrator. In this case, the orchestrator is more of a copyist for the final full-score.