Coming back from Africa recently (converting my ICAO-license), i might throw a little light on that subject.
1. FAA or JAR-license does not matter-you will have to sit the exam.
2. Depending on the country you are heading, you need to sit air law only, air law + met, or all subjects again.
3. Most african countries are referring to JAR-regulations; and some of them are using the Oxford syllabus for training and/or testing.
4. In most african countries you will need a type rating on a type that is already registered in the country you are heading for-to do a flight test.
So i would suggest:
1. Determine which country you are heading for to achieve the license.
2. Visit the CAA-page of this country.
3. Read their special regulations-or contact them, if you do not find them online..
Nevertheless-in most cases i know it took several weeks to several months for experienced pilots to complete the conversion....especially paperwork sometimes is a mess in africa....
Missing one minute in your log book because of a calculation error?
Everything is sent back and has to be requested again....paying for it again....