thank you! but i think thats still not the solution for me. i changed to “add up” plus “marker” - and that indeed helps laying out planes with varying opacity, while using different strokes, without making ugly overlapping edges - but: when it want to glaze over it with another color, the color is really saturated, no transparent look.
maybe the best solution is to use for ex. the awez wet brush with “add up” and “marker” to build up a foundation, and then switch to a new layer to glaze over with light, transparent color, and then later merge the layers…
edit: no … i does not work this way. i wrote this before i tried it out. now i have tried it. using another layer does not solve the problem, makes no difference…
looks like ONE brush ist not enough 
i will update here, if i find a good workflow for painting for me.