>>7743022
This is the brush I used, it’s slightly textured and square-ish. The opacity varied, but I usually kept it between 50 and 90 %, going full 100 % when I wanted to create a hard edge, such as the lips.
(the program is MediBang Paint Pro for Windows; brush sensitivity at 0.85)

(also sorry that it’s in (badly translated) German, but I hope this is still somewhat useful despite that)