Hi Fluidmotion,
This was possible back in the days (around a decade+ ago). Loading an abr file and done. I can't remember when I was asked that the last time. (I checked Cineversity in the previous Forum and nothing.)
Today a few things have changed; the most significant part is the Asset Browser.
Suppose you create a gray channel image of the brush tip in black, and a white background and load that into the Brush. Set up the most helpful parameter for this Brush and then Save Brush. In this way, it is native to Cinema 4D's Paint (BodyPaint 3D)
You can ask to get this abr import open back, "share your ideas."
https://www.maxon.net/en/support-center
All the best