Use to paint random colors inside your linework to be used as selection masks.
CLOW (a Masking Tool for Clip Studio Paint)

I just made this brush to make the 'Clown Pass' easier.
This is an advanced masking technique I use that separates all shapes of the drawing on a random color island that I can use as a selection mask.
Just set your line as reference layer and start dabbing on the different shapes of your drawing. Each dab paints a different color; shapes has no antialiasing so you can retrieve a clean mask from it.
The gif below is a timelapse in how to use it:

INSTRUCTIONS:
(1) It's important to set your linework as Reference Layer;
(2) When using the Clow brush, prefer a large brush size so it covers the entirety of a shape;
(3) The brush stays inside the lines automatically - just remember to place the brushstroke in the center of the shape; if you force paint outside, it'll.
(4) Each tap/brushstroke paints a new, random color
(5) The only option exposed in the subtool panel is Area Scaling; it increase the value if you want the colored shapes to "grow" behind the linework
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In this old video I tried to demonstrate how I'll use this Clown Pass technique.
It´s in Portuguese BUT you should get some idea from it.
-->> https://www.youtube.com/watch?v=P8hpzwjFKOs
-->> https://www.youtube.com/watch?v=P8hpzwjFKOs