Greg,
Your post brought back pleasant memories of my 1976 trip to Kenya and South Africa; because of politics of the time we didn't get to Zimbabwe (darn!). I'll have to get your video.
For my money the most impressive Garratts we saw were the 59th class in the EAR in Kenya. These maroon monsters had the same wheel arrangement, 4-8-2+2-8-4, but were much bigger than the South African GMAM class, although they were meter gauge rather than "Cape gauge" of 42". I got a cab ride on one of the 59s in the Nairobi yards. No sudden stops that time. In South Africa I enjoyed seeing the GMAMs on Lootsberg and Montague Passes as well as double-headed on an iron-ore line NE of Joberg whose name I can't recall. And the 2 footers were delightful; especially neat was a ride on an NGG16 with Billy Bester on the Estcourt-Weenan line; the engineer's seat would swivel outside of the cab so you could ride there where there was more room! Great view from there. Shot movies on that trip as well as slides; it was wonderful to see working "everyday" steam. I can still get that feeling at Chama, and even the smell of coal smoke is the same as it was in South Africa. (Of course Kenya steam was oil-burning, not coal; different atmosphere, not as pungent.)
Chris H.