FR3$H CONTENT.
brush variance is a really fun thing to play with when you figure out how to use it. with it, you can have a continually/randomly changing size, color, opacity, etc.
to actually view the brush variance sidebar, you'll want to right click anywhere on your toolbar. go to
palettes -
brush variance.

open up a new image and select the brush tool on the sidebar. by adjusting the numbers in the 'jitter' column, you can toggle how much you want things to change.
for instance, by upping the jitter of 'size', you get a pan out of small to large:

same goes for rotation...

and hue

you can continue to play around with these for the desired effect.