Level of privacy

I am superadmin of my little network of blogs.

I have "Allow Site Administrators to modify the privacy setting for their site(s). Note that Network Admins will always be able to edit site privacy options." set NO.
This is ok.

I set default setting "Only allow administrators of a site to view the site for which they are an admin. " This for me also OK.

The questuion is, how to change visibility for "Allow all visitors to all sites. , but Not as global setings. " I need for one site. One by one.

I would like open sites for all visitors one by one.
I see posibillity for "Only allow logged in users to see all sites"
but I would like open for all, not only for logged

I don't know how to do it.