bbPress

Setup your bbPress and/or WordPress installs as if they were fully integrated, they must be sharing the same user database table.

Make sure your cookies on all installs are set to the webroot of your site ( / ) and they are using dotted domains ( .example.com )

Edit near the top of cross-cookie.php and change the url to the OTHER bbpress/wordpress installation

Add the cross-cookie.php file to each install's plugin directory and activate

Make sure you tell WP-Cache to exclude any url with ?cc