I'll have to find the relant thread, dear Oriane, but I do remember that I used as much pressure as possible not to shift the underneath paint, but just to mix gently for the one on the same layer.
Not to low pressures though, so as not to loose the hue intensity. This is because with layers at high thinner rates I don't use the dry feature, so that some littl mixing blends and smoothes a little Anyway more or less around 30% if I'm not wrong.
For the glaze on an upper layer I gave sensibly higher pressures than 50%, because there's no problem and it keeps the glaze color vivid.
As for the thinner it's on the image and the loading was full loading in these cases.
Panta rei (everything flows)!