I did this YEARS ago. Like a solid 13 years ago. But I felt weird doing it and now it’s a method. I should have made a video doing it and then it would be my method not some femi method 😂 but when I did it I felt like I was cheating since It has the form over it and I haven’t done it since.
It could be pen pressure or it could also be the brush you’re using! In the video I’m using the “Basic-5 Size” brush found under the “Ink” section. If I were using the “Basic-1” brush, found right next to it, my ends would also be rounded! So try playing around with different brush types and see if that helps fix it! If it doesn’t, then it may be an issue with pressure sensitivity
