Two weeks ago we crossed through Brazzaville - Kinkala - Boko - Manianga - Luozi - Kimpese. It was smooth and easy (apart from an annoying drunk official on the DRC side who took forever to write some random things in a book).
The Luozi ferry can easily take a 4WD (they ship trucks back and forth without problem) and the road out to Kimpese is easy. I think the ferry is free too. When we crossed (on bikes) no-one asked us to pay, and it seemed like none of the passengers or the other car on board paid either.
Vladivostok - Denmark 2008... Finished.
Denmark - South Africa 2010-2011... Finished.