I've just seen a faux-hawked PT training a client outside my office. It's made me realised that there is a major flaw in my coaching so that considered, imagine that while typing this I am alternating between a suitably dramatic action pose and circling around my PC like a rabid wolf giving the impression I both care and also understand how the machine is working.
You don't want to be straining, huffing and puffing when you learn these. I don't believe KBs are quite as awkward to use as many practitioners make out, indeed I believe they actually facilitate certain movements and allow a fluidity missing from dbs. However, initially they can take some getting used to. In the TGU the weight is resting against your forearm and is therefore pulling you off balance. When I started I was pretty well practiced in doing the movements with much heavier dbs but I could not get up the first time with the weight in my left hand – I fixed this in less than a week. This brings us to stability. There are loads of resources from far more experienced individuals than me available on the internetz but what I have observed is the inability of people to lock their joints and keep completely rigid under the weight. I coach a lot of people with next to no history of putting weight over their heads and they really struggle to lock the weight out. One of the guys last year was furious because he couldn't do them despite being considerably stronger than I will ever be – too much bench not enough press. A lot of popular fitness culture also does its part to mess people up here with the tendency to discourage full ROM and locking joints out because it's apparently bad for you. Get that arm and keep it straight and tight.
What I would suggest as a useful tool is a pair of adjustable dbs, a 20kg set – these are cheap (although rising metal prices have pushed the costs up over here) and will serve many purposes. Start at 10kg and work up. I bought 2 8kg KB for the women I coach and there were useful at first but they grew out of them rapidly. They're still handy for pressing work but the 12kg pair see more action and a handful of the girls are using the 16kg and even the 20kg. Save your money for something heavier.
I think the 20kg is a really useful weight to have. It can be a big step up to the 24kg. I believe that Dan John says he uses the 20 more than anything else. I would recommend a 16-20-24 package (or progression) to anyone not of beastly proportions rather than the traditional jumps of 16-24-32.
Hope this helps.
The rationale for reduced gin intake and the knowledge of the perils of alcoholism and attendant metabolic derangement has almost entirely come from physicians and researchers.