I have an 8 hour wait for an international transfer at Johannesburg airport and will be changing airlines. I am very concerned about the stories of theft and tampering of luggage at this airport. How can I collect and recheck my bag when I am in transit? Then what do I do with the bag for that long? I want to plastic wrap the bag but am told that Australian airports do not have this service, is this true and can I do it myself at home before I leave?
At your source port, you can ask for it NOT to be checked all the way through. Just be open and honest and state that you're concerned about its security.
Make sure you can exit transit in Johannesburg though (have the right visa etc). Because the security may well be outside the transit area, and you may need to go through customs to get to it.
Alternatively you can do what I did in Kazakhstan when I realised my bag was not checked through, and I had no visa - I asked a friendly assistant, who kindly went out to the luggage hall, found my bag, and checked it in again for me. All went smoothly, thank goodness.
I've traveled through Johannesburg many times on international connections and have always checked my bag through without incident and have many friends and colleagues who have done the same without problems. That being said, Johannesburg airport did have a reputation for bagging pilfering.
If you want to re-check your bag in Johannesburg, you will need to tell the check-in agent at your point of departure to tag the bag only to Johannesburg. After arriving in Johannesburg, you will need to go through passport control (instead of international connections) pick up your bag and clear customs. Then you will need to return to the departure hall and re-check your bag with the connecting airline. Immigration formalities in Johannesburg are relatively quick, but I wouldn't attempt this with less than two hours between flights.