One thing I’ve wanted for a while in Illustrator is the ability to randomly choose brushes. I finally wrote a script to make it happen.
So now you can draw a bunch of paths in, say, a “dying marker” brush, then decide it looks too obviously fake, make a few more (“dying marker 2/3/4…”), and randomize them.
Or you might make a “lovely fir tree” brush, draw a bunch of lines with it, then decide you want some variety and make a “lovely spruce tree” and “lovely larch tree” brush as well, and randomize them as well. Though if you added a “lovely sycamore tree” brush, the amount of name difference you’d have to allow for that one would probably end up selecting from almost every brush you had in the document. That’s what undo is for. And temporary brush renamings.
If this feels like a thing you could use then grab it here and put it in the scripts directory of your copy of Illustrator. Enjoy!