Using more tag to protect different access level content

After going through the videos and these forums, I'm still not clear on the use of protected content so I hope someone can clarify it for me.

If I have 2 access levels:

1) Free to use - Registered members.
2) Paid for - Premium membership.

I have 2 articles:
1) available to all registered users (not visitors).
2) premium content for paying users only.

To acheive this I think I need to use the more tag in both articles to encourage site visitors to register and secondly for registered users to upgrade to paying membership.

I then need to add a positive rule for the more tag for both levels in membership. BUT how does the more tag/membership know the difference between them?

Or can the more tag only be used for one level?

ALSO

On the Content Protection Options page in membership, the first area is to add a Protected content message, if I use both this shortcode and the more tag, both messages appear on the post.

I'm confused, what I am doing wrong :slight_frown:

Best wishes
Jane