There is no such method. I have tried to figure out the answer to the same question for almost 4 months. One of the higher dans I have approached for an answer has told me he has done 0 tsumego, another told me he brute-forced them (I have yet to run into a dan that actually did tsumego practice in the recommended way). Some high sdks/dans told me that there is no point to replaying/watching pro games at ddk while others insisted I follow pro games. I have also played against better players, got my games analyzed but to little use cuz I get lost in the endless variations the reviewer plays and the tree becomes such a mess in the end, there is little chance of going over it to understand it better - reviews often feel more like for reviewer’s benefit than the newbie’s, especially when there is not enough chatter during.
Tsumego - easy to find sites for, easy to find lots of to keep yourself busy in small windows of opportunity during the day - improves shape recognition if you bruteforce, reading practice if you actually try to solve them (often a slow and frustrating process).
9x9 - quick, easy to play games for busy people - you learn certain techniques but there are too many of them (and too much complexity to them) to be deduced from random board play.
Learning Pro game - Memorizing pro games is possible and meaningful when you can understand the train of thought behind the moves. For beginners, it is just for seeing what high level moves look like and to understand what is so basic that you even see at pro level (like connection vs a peep, endgame sequences).
I have never tried one-color, blind-go or sunjang baduk and I don’t know of many who do,
not to improve anyway.
Even though I consider myself to have failed at finding such a method, if I would recommend anything, it’d be playing 9x9, doing tsumego (bruteforce if you get bored) as per common advice - BUT on top of that,
1- find a player around your rank (or higher if he is into it) to play games in which you talk about and explore sequences and undo while you play.
2- find people who can teach you and get lectures about specific topics, (like probes, connecting over/under) Once a better player shows you a sequence, it’ll get etched to your memory and become a useful tool during certain situations in your games, which’ll lead to you automatically seeing/playing certain sequences and having time/energy to read other ones you’re not sure of.
These 2 methods differ from the others in the sense that it is not entirely up to you to be able to accomplish this. You need find a good newbie to play with and a good teacher you can understand and learn from. Not much convenience to them but they are very advantageous.