How to protect site content from 'non' members

Can anybody suggest an easy touch light weight method to protect entire the content of our ‘Ideas’ site to anybody than non members.
There is an exception, I still need to have the login page unprotected and I would like a selection of posts that appear on the front page to remain unlocked.
I have been through many membership plugins, some very complicated but they just don’t seam to do it for me.
The WPMU membership plugin that I have sued on other sites, just donst appear to lock down any of the IdeaStream content !
The other extream, WP-Members just appears to lock the world down even my few posts that I want to keep unlocked.

Any suggestions warmly received.

kindest
Andrew

https://www.ads-software.com/plugins/wp-idea-stream/