Hi Nick,
Good to see that you are treating this as an experiment. You should try as many suggestions as you can get and use what suits you best.
What I have described above works for me (for now; I am also open to change) but I may not have done a good enough job of describing the whole process so I will try to add some explanations here.
I would like to clear up a couple of things. One is why you need to play at speed (meaning at indicated speed) right away and another is why the repetitions. But before that, let's get the definition of technique out of the way first. I realize that technique is something that has as many definitions as there are people trying to define it. Nevertheless, I will try to describe what I understand technique to mean.
To me technique is the sequence of movements made by the music making (or piano playing) mechanism i.e. our fingers, hands, forearms, upper arms, shoulders and even the rest of the body like chest muscles, diaphragm, back muscles, the gluteaus maximus (yeah, that would be your butt) and down to the legs to bring about a 'proper' execution of the music score in front of us. Included in 'technique' is the musical aspect of the piece (interpretation) i.e. if the dynamics call for cresc. then the 'technique' that you use must enable you to play cresc. Technique must also allow you to do phrasing, slurs, legato, etc. that is to say the totality of the music you are playing.
Well, what are these movements? There are various names given to certain movements and some say there are thousands or hundreds of thousands of techniques. Gyorgy Sandor in his book 'On Piano Playing' groups them into 5 main groups and talks about combinations of them so I guess that would account for the thousands. They are i) free fall (or gravity drop), ii) five-fingers, scales and arpeggios, iii) rotation, iv) staccato, and v) thrust.
Of course, how each of us go about executing these movements depends on our physique, some of us are endomorphs, some are ectomorphs, some have fleshy palms or thick wrists, some have skinny wrists etc. All these will determine how each of us go about executing those movements or combinations of them. But (and this is very important) the aim of good technique is to hit the keys in such a way that there is no or minimal tension in the piano playing mechanism. This is the over-arching requirement in the search for the 'correct' technique when we approach any piece of music.
Now back to the 2 questions. First, why play at indicated speed as soon as possible? Because the sequence of movements required to play the notes in front of you allegro is different from the sequence of movements required to play the same notes andante or lento. That's why it is not recommended to play a piece slowly HT and then ramp up the speed on the metronome. At a certain point, you will not be able to go any faster. That would be the speed wall and indications would be pain in the playing mechanism typically in the forearms or the back of the hands (sometimes in the shoulders too but definitely not in the butt, that would be caused by a third party like someone talking too much... gulp!)
Now, when you attempt to play at speed the first few times you will fumble and fail because you have not discovered the 'correct' sequence of movements that is required. As you experiment, you try different hand positions. For example the music requires you to go from white keys to black keys. Well, you would need to raise your forearm a little by moving your elbow out slightly. If you are playing broken thirds it will help if you rotate your wrist as you move from low note to high note. And so on and so forth. After a few fumbles you will discover the sequence of movements that will enable you to play that bar, phrase etc at speed with no or minimal tension in your playing mechanism. Now this is what you need to practice.
And this brings us nicely to the second questinon. Why repeat (almost) endlessly? Because you need to remember what the sequence of movements are and more importantly you need to condition your hands to move that way properly. This is different from the endless repetition of Hanon which may be harmful to you if not handled thoughtfully. Conditioning is the key word here. So when I say repeat I assume that you have already discovered the 'correct' sequence of movement for that bar, phrase etc. The sleep in between practice reinforces this conditioning.
Now I'm not sure I understand what you mean by getting lighter and lighter as you practice. Do you mean softer? Since you are not getting the sound that you want it could be that you are not using the 'correct' sequence of movements to make that sound. Experiment some more at speed HS to see if you can get it. That is what I mean by interpretation must be included in the search for the 'correct' technique. If a big sound is called for then the sequence of movements required for that part must allow you to do just that, make a big sound.
I'm not sure what you mean by weight transference. I have heard about the weight method and I noticed you started a thread on that but it went way over my head. Sorry.
Okay, that's about all I have in mind to say for now. I hope I've been of help.
Regards,
dennis lee