i was also a quantel artist for many years and remember the soft dithering that it produced...
some effects do have a similar technique... the ramp effect for instance has a 'ramp scatter' property to that can be adjusted when it produces banding.
adding noise or grain (as you mentioned) is a way to reduce banding more universally by effectively creating dither.
greyscalegorilla shows another method that adds tonal variation to reduce banding:
http://greyscalegorilla.com/blog/2009/10/how-to-remove-banding-artifacts-in...
genarts also has an effect called 'deband'.
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW
