Del123
there was that one where kakashi did a one handed hand stand on a kunai for a few hours and you can always have him do leaf and tree-water walking at the same time or you could stick heavier things to the body than leaves. maybe water walk on fast moving water or up a waterfall? idk visit the multiple reddits
I’m pretty sure other than rasangan the best way to train chakra control is through training medical ninjutsu (which is best for him at the moment as he could be under roots or hiruzens watch and he couldn’t know how to make the rasangan but medical ninjutsu would also be useful for training with Guy and is useful in general if he becomes good enough he could follow the trope of training under tsunade which with her unique jutsu would go perfect with Guys 8 gates definitely with no other motives including wooing her like any good disciple of hers would). I read somewhere that tsunade makes her disciples hang onto a tree with one finger to train chakra control though it could have been another fanfic. (I hope this help in some way)