Display a single post on a publishing site

I am using a Content Query Web Part to display Blog posts on my homepage(a publishing site). My question is how can I

1. Compose my post URL to point to another sub-site(a publishing site also) and make the post content be displayed in a content query web part.


2. Use the Content Query Web Part pick the post_id from the URL

E.g user clicks on this url

        <a href="http://domain/publishingsubsite?post_id=4">Read More</a>

The post_id is picked by my sub-site and displayed with a content query webpart