It was not somehow special training, I would even say a lazy one. I managed to complete the start of the mentioned 6b on the negative slope balcony, and even almost finished the whole trace after that. Also tried number of other 6a+/6b traces on the vertical wall and some gym exercises for the back.

Old problem still persists - I become tired very quickly so subsequent movements or new traces, if require at least some force, will be usually completed with falls. I will work on it with the exercises, but I do not expect power endurance to appear quickly.

So, to date, I have a quite strong technique level, I would say that I could complete 7a traces (I even did that on the vertical wall for couple of traces 2 years ago), but my power endurance is miserable, so I can not climb even 6a easily on the negative slope (I can usually do 6a on-sight on the vertical wall though, couple of times I managed to complete 6b traces on-sight, but that is rather an exception). But after some work on the trace I usually can move on 6a-6b on the negative slope, but it requires really lot of work to memorize the holds and body moves.

So, next milestone is scheduled to be a power endurance and static load improvement. I expect it to be achieved by special gym and climbing exercises, and would like if its rates are similar to what I got for muscle power improvements.

But we will see... I feel summer will be busy.