The gold standard of population control is easy access to birth control and education of women.
In every country where either of these have been implemented, the birth rate has plummeted whether that was the intended effect or not. In countries that have implemented both, birth rates have generally fallen below the replacement rate.
The current population boom in Africa can be traced back to the George W. Bush administration, which cut birth control aid to Africa in an effort to promote abstinence-only birth control for muh morals.
If you want less Africans, give them birth control. It's not rocket science. Chemists did all the hard work.