in 2009 I just wend to Berlin, to their Ambassy, asked for a 6 weeks visa, gave him 50 € took the stamp and left, in NDJ I got it extendet again and again ... no problem ... but there is one big BUT, I was working for a big oil comp ... so the goverment wanted to have me there ...
But the guys in Berlin are super relaxed, if you have the chance just go there, French would help too, anyway there you have to speak French.
But why to go to Chad? Spend there 4 Month, didnt like it that much, actually not at all (except the people) ... Try to avoid the rain season!