The disinvestment campaign did very little except transfer ownership of some of the largest companies in the country to South Africans and I would assume the bulk of that would have ended up in the hands of the politically connected.
Sanctions also didn't do much. There was a thriving market for goods from overseas. Even now more than 30 years later there's a tradition of giving your relatives a list of things to buy when they travel internationally. Sanctions probably indirectly hurt poor South Africans but never anyone politically connected.
What really hurt and forced the Apartheid government to start seeing sense was the IMF ending all loans. http://kora.matrix.msu.edu/files/50/304/32-130-4C3-84-africa...
I think the Swift banking system ban proposal for Russia would be more likely to work.
https://en.m.wikipedia.org/wiki/Disinvestment_from_South_Afr...