(I typed this reply as Mosis was typing, but to add to what he said)
Well I think Barnhard and Chang are probably more qualified to give you specific answers to this specific question, but I'll try from my understanding.
Now, I wouldn't be able to play these (if they were new to me) full speed first, before any kind previous slow speed practice. Were you?
I would if I didn't try to to take such a big chunk.
I'd look at the first bar. The first two beats are the same, and I'd probably end up using a repeated note group to get the notes all in my hand (search on 'repeated note group' if you don't know what that is.) Starting with only 2 notes, yes, I could do it at speed=infinity. so could you. Play them together. A-Bb probably with fingers 4-5. Sound them together, and then use what Chang calls "Phase angle" with regard to a parallel set, Bernhard calls it "wiggle your wrist" to ever so slightly alter the time between when 4 hits the A and the 5 hits the Bb. Alter this "wiggle" to slow it down (from speed=infinity). You could do hundreds of repetitions of that bit in a very short time. Then from Bb to A (54) it would be the same motion in reverse. Don't use your fingers, use your forearms, wrist to "roll" from one note to the other (sounding them together as a "chord attack" first equaling speed=infinity, and then changing how you roll from one to the other to slow it down. You're not speeding anything up, you are starting as fast as possible and slowing down. easier huh?)
To do a full repeated note group, if I labeled those first 6 notes 1-6, you'd practice just that, starting at a chord (speed=infinity) and slowing down to very slow and speeding back up for as long as it takes to master that chunk. You'd repeat for:
12
23
34
45
56
123
234
345
456
1234
2345
3456
12345
23456
123456
Doing the fast to slow to master each "group" - complete the entire set in one sitting, and you have just executed a "repeated note group set" exercise for that.
You may already have technique that makes it very easy though for you play that kind of motion, so it's up to you to decide if you need to do that or not. But with this kind of phrase, it's all going to be in your rolling that wrist, not executing the notes with your fingers, rather, letting your fingers simply be an extension of your arm.
Anyway - it may also help to not necessarilly think of those groups of 6 as starting and ending as they are written, perhaps the group should be played crossing the bar line (ie. take all those notes, rewrite them, and shift all the connecting lines over so they cross the bar line, so your groups of 6 cross the beat. I don't know if this will work for this piece specifically, but it is something you should try and see.)
I see alot of repetition in that right hand phrasing. The same shape repeating over and over with a few accidentals, starting on a slightly different note, so keep that in mind. If you master the motion and learn the few differences in each group of 6, I think you could learn to play that entire passage, at blinding speed, very quickly.
If you start too slow, you could easilly give more emphasis on the notes coming from your fingers, or any number of hand movements that will allow you to play a beatiful version of this passage slowly, and you would then start speeding that up, but you will hit a "speed wall" at which point those motions which you have now (unfortunately) ingrained in your subconscious, will not allow you to surpas. You can see (I hope) how this concept of starting at speed=infinity (even though it means starting with as few as 2 notes) means you only have to worry about slowing down. What is easier? Slowing down or speeding up?

understand I can cut the chunks to just two notes, but two notes by two notes it would require me three years to finish these pieces as they're made of thousands of notes
This is not true. Hopefully, seeing the example above of the repeated note group (as an example, you don't have to do an entire set like that for every phrase) - but you can get hundreds of repetitions into a very small amount of time. (as an aside, be sure when you're working on this type of thing, that you find an equally challenging passage with your left hand, from the same piece or an all together different piece, so you can alternate so as to avoid injury.)
Also, as can be seen in your first example, yes, there are 24 notes or whatever, but how many of them are unique and require unique motions to learn? Very few. You have to look for patterns and look for ways of pulling from a score what you need to learn, and what you can "imply is learned" simply because it's repeated.
Anyway, I don't feel I'm doing any of these techniques justice, it's all described at length in posts by Bernhard and in Chang's book, so I guess I'll stop writing. I hope this has helped somewhat!

-Paul