Using an airbrush eraser gives a different fade, which it doesn't suits well, that's why I used parallel gradiation to make a perfect fade Edit: pinning this to let people know why I use parallel gradiation than airbrush eraser
you can also do the two ovals, one on top one on bottom, clipping mask and make the color the color of the circle/object ur drawing on, half that color and white, gaussian blur and lower opacity