Typical career routes
No matter how highly qualified they are, the majority of Re-Recording Mixers start their careers at junior levels (usually as Runners) working for one of the Audio Post Production Houses. Experienced Re-Recording Mixers look out for those who show talent and a co-operative attitude and bring them into the mixing studio to train as Assistant Re-Recording Mixers, providing general studio support, recording Foleys etc. After several years, Post Production Houses usually promote the most competent Assistants to become Re-Recording Mixers.
No matter how highly qualified they are, the majority of Re-Recording Mixers start their careers at junior levels (usually as Runners) working for one of the Audio Post Production Houses. Experienced Re-Recording Mixers look out for those who show talent and a co-operative attitude and bring them into the mixing studio to train as Assistant Re-Recording Mixers, providing general studio support, recording Foleys etc. After several years, Post Production Houses usually promote the most competent Assistants to become Re-Recording Mixers.
Setting the relative volume levels and positioning these sounds is an art form in its own right, requiring the skill and aesthetic judgement provided by experienced Re-recording Mixers. Because of changes in technology, many jobs in sound post production are less easily defined, e.g., on some small to medium budget films, Re-Recording Mixers may also work as Sound Designers.
Although they are usually employed by Audio Post Production Houses, Re-recording Mixers may also work on a freelance basis. They work extremely long hours under considerable pressure, and usually work on both film and television drama productions.
http://www.skillset.org/film/jobs/post_production_sound/article_4764_1.asp