Did the the same trip in 2007/2008. As far as i know the only place to get the Angola visa comming from the South is S. Africa. We heard from others it took them more than 6 weeks.
We did the west side first. The only place to get a 5 day's transit visa is Matadi. When you go to the ambassy in the mornig you'll have it in the afternoon. (Dress propperly!!!! Otherwise they will refuged enterance!!).
It took us 7 day's to get to Namibia. No problem at the border, they didn't even mention it.
We have been to other embassies along the way. This is useless. They will not issue it.