A soft-edge rendering brush!
The Softaloct Brush!
A soft-edge brush, by Cephaloct!

This is the brush I use for most of my rendering. Shadows, highlights, bases— you name it, and this brush does it. I use it alongside my lineart pen, which is the Cephalush Pen, and a hard-edge airbrush.
The results look something like this!:

I hope you try out the brush and enjoy it!
Examples were drawn on 2000 x 2000px canvases, with 300dpi.