I think you will find that a better period than an other matters only if you go to places where there is some kind of seasonal work.
What I mean is that places with a tourist industry (Zim,Bots,etc..) will lose pilots towards the end or in between seasons (Dec-Feb).
Places where oil, mining etc... provide most of the work, will lose pilots and gain some all year round. Since you have mentioned KIN,LBV and Douala, you will be interested in knowing that those places don't offer much in terms of tourism (to say the least
).
But the good news is of course that aviation is quite lively (needed) so you could well be lucky.
Also since almost anything is possible in Africa, 400 hours could land you any kind of work. Just a matter of hanging on until it happens.
Good Luck