Re: Assingment to large and groups and subgroups

It sounds like you need the cohort function

http://docs.moodle.org/22/en/Cohorts

An alternative might be to set up meta courses - you enrol the staff on the HR course, the Sales-USA course or the Sales-Asia course as appropriate and then when you are setting up new courses, you use the meta-links enrolment method to populate the user list.

http://docs.moodle.org/24/en/Course_meta_link

HTH

Richard