Reading your question and knowing that you're an Akuzawa guy, I suddenly thought to ask what Akuzawa might possibly do for down-weighting situations like you're describing. I know that he has the "push-out" thing you mentioned above (for groundpath stuff) and I was wondering if he also had something similar to practice for down-weighting?
I haven't been to Tokyo in 2 years, so what I write below is my own interpretation of what I think Ark's exercises are supposed to teach for down-weight. I can't recall in class or seminars, Akuzawa explicitly saying that these exercises were for down weighting, but on the other hand he has his own lexicography. At the moment I'm thinking that utilizing gravity is really what this "heaviness" feels like, but it is a centered gravity, not a leaning off balanced use of gravity. I'm not 100% sure if what I am doing right now is considered "down power" or "down weighting", so clarification of the term would help me figure out if we are talking about the same thing or not.
Note, some of these videos are done by students rather than Akuzawa and for illustrative purposes of the general shape of things. Unless performed by Akuzawa I wouldn't inherently consider them "correct"..
Mabu: Horse stance with arms stretched out forwards. Hands must stay heavy. If the shoulders engage they wont be heavy. If you watch Akuzawa's videos he goes around to check for this by taping/pushing on the palms. If the shoulders are holding up the arms and not relaxed, the person's shoulders jerk back when the palms are hit. If they are relaxed that push seems to travel down to the foot and the upper body doesn't move. Other than when you initially raise the arms, I don't see an open/close movement
Analagous to your universal exercise, though I certainly do not utilize a breath powered version yet as I focus soley on connecting the arms to the middle and keeping the hands "heavy" throughout the movement. I also add the "scissor jack" type movement discussed above, while sort of driving the kua area down in the front and using the back of the thigh to kind of push upwards. This causes an open to initiate the raise of the arms. Likewise when lowering the arms, you "sit" into it to initate a close to bring the arms down. If the arms remain heavy, someone should be able to push on them the whole way down without your shoulder kicking in to push back.
Shiko (legs need to keep the weight in them): the sumo stomp, but no focus on stomping into the ground, rather keeping weight in the legs causes the upper body to tilt over. I focus a lot more on keeping both of the feet heavy (and hands supported by the middle and heavy) instead of moving tension/pressure around the upper body. This drives the "lifting leg" outwards and initates the tilt over. Wether you are doing a linear or "winding" version of shiko (which I can not do), maintaining this heavyness at all times, and initiating the raises and lowering of the body and resultant arm movement by folding the kua/scissors movement seems to be required.
Mabu walking (Looks like a variation of Forrest Chang's I Dream of Jeannie exercise)
For all of these exercises, at a starting point at least you have to keep the hands/arms "heavy". This does not mean pushing the arms down with the shoulders to make them heavy, but requires that the arms and shoulders are relaxed. Therefore something else must be pushing keeping them held upright. In partner training this could be your partner in the manner I discussed in my initial post, which is not a bad starting point if you are new to this sort of training. For solo training, I tried to lay some of it out above, but feel there is a high probability that my point would not get across properly. None the less, I think in order to do any of these exercises correctly beyond an initial stage, they need to be preformed with more than just relaxing the upper body, but rather supporting from the lower middle area.
I don't seem to actively open or close the upper part of the body for these exercises, though the kua opens and closes as part of driving the weight of the leg from back to front as you step forwards. You could of course close the upper body for walking mabu while keeping weight in the arms to "win" to take your partners balance and then maintain that and move more quickly, but one easily could get sidetracked on winning.
Now a while back on a different forum, you had mentioned that you thought some of these exercises were fairly advanced. I disagreed at the time as I was in fact doing them wrong, and now I have to say I would agree. There are simpler ways of getting your foot in the door for establishing ground paths, or learning how to relax your weight onto your opponent than the aunkai exercises. I'm not saying they are bad exercises by any means, you can just wind up working the wrong muscle groups if you don't have direct feedback from a teacher/partner who knows, or don't nearly think about it enough yourself. I had to start all over again about a year back to figure that out.
Alex has us do a number of simplified versions or warm ups prior to doing the actual aunkai exercises. Some of them are as simple as a very simple tenchijin. Essentially doing the whole getting under your hands thing I have spoke about in other posts (opening/forcing the kua down, and lengthing the backs of the legs) then simply relaxing and dropping your arms once your arms are over head. I don't pull the arms down, just let the force of gravity drop them down like if you dropped a wound up chain. You could of course add to the force of gravity with the dropped arms by closing, but I haven't been practicing that way.
If you can at least relax onto your opponent for pushout, pushout changes dramatically, for both partners as I spoke of in the manner in my original post. For a long time I merely pushed my arms out from the shoulder in a straight line. Now by relaxing the make an arc like a swinging pendulum. I can add to it, taking the weight of my opponent and arms into the crotch and by kind of pushing outwards/forwards from the kua/ top of the thigh right below the crotch to drive the arms forwards.
Before I discuss walking mabu in more depth, as a matter of form, the walking mabu exercise generally is preformed differently with both partners arms outstretched, or both bent and relaxed. None the less, it can be preformed by resting bodyweight onto your opponent, forcing them to hold you up muscularly or by countering by relaxing their weight back onto you resulting in equilibrium. Of course you have to add to it, by figuring out how to shift bodyweight from foot to foot, and resting your bodyweight+your opponents onto the kua area, down to the ground and rebounding back up.
Any feedback is kindly appreciated,