Heartily concur with IO's advice re the uniform. We're just back from a 3 week aero safari of S Africa, Botswana & Zambia and were advised by the locals to wear pilot shirts & epaulettes.
Felt a bit of a phony in the 'uniform' at the Maun (Botswana) AIS office when asked what I was flying by a British PC12 charter pilot and admitted it was a C182
Decided not to wear the uniform after that, but thereafter had far more hassles with both immigration and customs.
No problems with visas for S Africa or Botswana, though we obtained visas for Zambia beforehand. Another point re Zambia - you have to obtain clearance for any flight in Zambia from their Air Force at least 24 hours beforehand.
Make sure you take an Air BP card for fuel too - they seem to have the monopoly for most of Southern Africa.