hi nibile!
in my limited empirical experience you are on the right way.
the science would say that you only want to train things that will recover in 24hrs (or less). So neuromuscular or technical stuff.
short, intense session.
or even better, low volume, intense, with really long rests in between moves/hangs/exercises.
as for when to stop, my personal guideline (no science) is that i stop when i feel that i've reached 90% of maximal for the day, and from that point onwards i can only manage roughly the same intensity, or worse.
It has to be a bit hard to stop, like "hey wait, it was just starting to get fun...".
Saves motivation too...
exercise idea: hang in an open lockoff position for 2 secs, get angry and pull up as fast as you can as if you wanted to headbutt the ceiling
(be careful - fully warmed up, not too many reps, not on a dangerous hold, etc)
this kind of session works even better if you can climb on some kind of support and replicate some of the flavour of next day's climbing - just stripped of any pumpy/fatigue element.
(same holds, moves, pacing, etc... but climbed in segments, if it's anything longer than 3 moves)
other rule of thumb: for some reason on the second day i always tend to have better endurance than what i felt the day before, and maybe a little less power if the 1st day session was quite long.
(this is very obvious on traverses or roped stuff...barely doing the crux, but wait...how comes i don't get as pumped as i would expect?)
of course all of this matters if you bother being strong tomorrow, if not you can get as trashed as you want today
last tip if you want to get anal (in more than one sense?)
on day minus one and minus two, eat low-fiber.
you'll shit less at the crag, you'll be less "gonfio" and maybe a few hundreds grams lighter.
