To give you some background: I am UK and US citizen. I spent 4 months in Africa last year, I am married to a Kenyan.
In Africa, if a company needs you, they will find a way to get you the right visa/work permit to get you working.
However, in much of Africa there is high unemployment, so governments are not quick to give such permits/visas, and companies must first employ citizens of the country.
In places like Namibia and Botswana, expats (people who are not citizens of the country) are often hired to fill positions in aviation.
In Maun, for example, the companies there have been hiring from 10 to 25 expats every year for the past 40 years.
In Namibia, companies have been hiring between 4 and 15 every year, for the past 30 years.
In both of these countries, they've generally hired pilots with 250 hours. Lately, due to unemployment pressures, this has raised to 400 or 500 hours, again depending upon need and availability.
In places like Zimbabwe, Tanzania, and Malawi, they hire pilots with 1000+ hours, usually these are pilots who've done a year or two in Botswana or Namibia.
In other countries, the minimum hours go up, as in 2000+ or 3000+ AFRICAN experience before you'lll get hired (unless you are a citizen of that country).
There are lots of reasons for this, but really, if you think about it, flying in Maun is in and out of dirt strips at 3000' elevation, whereas other African countries can be 10,000' elevation, mountainous terrain, jungles, etc. etc.
When I was in Namibia, there was ONE company that was looking to hire instructors, and they were desperate, and would have taken anyone from any country at the time - they've since hired several instructors and are no longer in the market.
All of Africa works different to the rest of the world. In order to get a job in Africa, unless you've got thousands of hours and are rated on 'big iron' you will have to be there, show up at the door, present your resume/CV and get to know the chief pilot or owner of the company.