@Rangen
A bit late to the party, lots of good things said, but saw your post early afternoon as I was working on a few knives, so I took the liberty to document a few things for you along the way. I'll try to be fast.
As already said and the most important thing, the height at which you can work comfortably. In my case I have to boost my stone holder + stone height with a brick, and my pan is also propped on two cork antislips that are almost 10mm thick. Won't talk numbers exactly, but I'm tall and that is what it takes.
My body touching the countertop because I could basically picture than I'm naturally holding my hand at elbow height. In sharpening, I would say, shoulders are the propellers, elbows are the hinges, and wrists are the clamps - or locks or whatever. Thinning is the same.
Sorry for the grainy shot, switched to front camera, and still not an easy picture to stabilize at arm's length. But you can easily see this space as fitting a stone and a knife at an angle and be about natural height.
But I focus on this to mostly say this tip: when sharpening or thinning, you do not want to hunch over, or have your hands raised lower. Both instances adding unnecessary tension to the neck and shoulder, as well as making your body want to naturally "lean onto" to shift the weight over. So my best tip is that before you should start anything, you should rather straighten your back, your neck, and prop your shoulders just a bit backwards - the proud stance, you know. That achieves a lot of things: it's easier to breathe, and you feel steady, and you're naturally adopting about as much strain as your shoulders can take without feeling any tension - thus describing as much as you want them to move backwards in sharpening, since it's much less strenuous to rather go forwards using the natural extension of your arms. You're also telling your body that the movement you intend to make is no leaning into, but a back and forth. You are essentially absolving it from having an influence in what is to come - only the propellers, hinges and clamps will work and define the weight shifted down your work.
Now in the proud stance, move the system back and forth. I gather that you would want your fingertips naturally getting to about mid stone at most - since naturally it's easier on the system to keep your elbows at your body backwards and just move them forward and back to inertia. So from the stance I took in picturing my above props, or this picture for sakes of equity to the similar picture above as well as to show my usual distance to the countertop -like 8 inches almost exactly quite naturally either in cutting sharpening or thinning...
I push back the so-called sharpening station enough to get the natural inertia point where I want it to be.
And put my fingers on the balance as I'd do in sharpening, with no further tension to the shoulders-elbows-wrists systems. My ugly reddish skin (sorry eczema, dishes, sharpening, and a lot of trips outside at -10*C in between) will be particularly helpful as we shall be able to track applied pressure just from the already greyish and swollen joint and knuckle of my two most powerful and authoritative fingers outside the essential thumb - further whitening there is equal to a real pressure I apply with the fingers mostly, and as different as what I'm about to try and show next.
Ok, no scientific experiment... What I want to show is how easy you can apply "pressure" without pressurizing the system anywhere as much. In fact, as unscientific as it is, in the next example I really tried to imagine a knife and a stone. I just did a complete thinning yesterday and today I resharpened that knife, so the balance prop setup and finger placement is really in just getting back the particular physical stance.
So this is the natural sharpening "pressure" - 111g. Proud shoulders, inertia point, notice the relaxed and offset from center of the balance positioning of my fingers there, as if exactly "following along" something. In "thinning" this would rather represent the "most force" I'd apply in further polishing a bevel.
See the knuckles? No much whitening but from further flex. This is the most important. In this picture I am simply "tensing" the hinges to clamps point. The forearm. My fingers naturally adopt a position that will at once receive that extra tension without fatiguing as much as they would keeping them in the relaxed position... but much more importantly, a natural adaptation to finger burns and applying the tension where you want it. About 250g in pressure simply tensing that section and angling my fingers to transmit it stably and forwardly.
Still no further whitening of any knuckle. Now the tension is applied to the full system. From shoulders to wrists, fingers adopting the same position and place. I'm applying near to a pound of pressure now just by tensing the system. Yet this is no straining. It feels like the difference between holding nothing and holding one pound of meat.
In real life, the 250g pressure might be when I'm cutting a fresh bevel, doing a relief bevel, thinning/shaping, on something that's already pretty good. A better image would be the difference I tend to apply between the forward tip area vs. the heel area in thinning generally - usually getting the tip a bit thinner without having to break out of a full bevel motion.
The full pound of pressure feels like working a really thick crappy steel knife - on Imanishi 200 no less - just trying to inculcate it a edge shape I can much more easily follow and fine tune on a more behaved stone - but it's what is needed to get that shape without spending much time, nor straining myself over it.
. Any job you do is physical, you need to work in a good position whatever you do.
