Is there a hotkey to switch between Add & Subtract Brushes?
Not as far as I know, but you can, press W and quickly change your Weight between 0 and 1.
Hi Bryan, no there isn't, but Demeter (Blender Studio) has written an add-on that does this.
https://gitlab.com/blender/easy_weight
I think there is a demo on the Blender Cloud.
It basically changes the brushes to hotkeys 1 2 3 (add subtract blur)
I don't know if this is new for Blender 4.1, but you can achieve this by pressing CTRL while painting, whether in Add or Subtract mode.
(It doesn't switch the brush per se, but it toggles the brush function, so personally I only use the Add brush and press CTRL whenever I need to subtract values)
Oh thanks Bahia bbarbvibesonly ,
I didn't know that worked in Weight painting as well.
I just checked and it is new, since Blender 4.0.