Smudge tool for bitmap art

I have been experimenting with creating digital painted artwork in Toonboom using bitmap tools and similar process as when creating works in photoshop/ procreate.

Results have been great so far, better than I imagined.
I truly feel the bitmap tools are top notch/ in my point of view they even exceed TVPaint which is a software dedicated to bitmap animation.

When I create digital painted art, I usually create line work and rough tonal work in charcoal pencil (grey or brown) and then using airbrush and smudge tool, I smooth out to create planes with smooth gradiation. I then apply a colourise layer on top of all this and add the final colours of the object.

My suggestion would be to introduce a smudge tool for bitmap artwork in order to help smooth out painterly strokes and create smooth gradiations of tone.