Manually adding Subscribers to an ezmlm list

Hi all, I am new to this list. Please let me know if this is not the right
place to ask this question.

We currently use a web based form to send out mailings to our users. We have
about 2000+ users in our list and need a way to manage the list with more
accuracy. We have installed and setup ezmlm for this task.

We first want to add all our current users to the list and then give them
the control to unsubscribe at their discretion. 

How would we go about adding our current 2000+ users as subscribers to the
list?

We also need a way for any new users that signs up at our site to be
automatically added to the list. How could we setup a procedure that would
allow for any new users to be added to the mailing list as they sign up or
some sort of cron job that does it on a daily basis?

We have researched the way ezmlm stores its subscribers in the ~/subscribers
folder. We thought it would be as simple as adding all our users to one
single file, but it seems that ezmlm uses a hashed(?) naming convention to
store text files with all the subscribers.

Would it work to just add all the users to one of the text files? Or do we
need to break it up into separate files? Any other suggestions?

Also, could a perl script or something running on a daily cron job do the
trick to pull a list of new users to the site to be subscribed to the list?

Any help would be much appreciated. Thank you in advance.

Respectfully,

Daren Sabin
[email protected]