How can I make a brush with low opacity that increase its opacity within a single stroke?

The first image is from MediBang, where a watercolor (& most other) brush with low opacity layers over itself within the same stroke. The second image is from Infinite Painter, where absolutely all the brushes I tested, when their opacity is lowered, cannot exceed their own opacity within a single stroke. To achieve a similar effect, I either have to make multiple strokes with low opacity or change my drawing style & use the smudge tool.

Please help 🙏