Ok, so I let a specific someone use the trackball on my computer, while they were moisturizing/oiling their face/hair.

And now I’m stuck with an overly oily trackball ball.

This sucks.
You know who you are … :-(

Time to get out the 40% solution of Isopropyl alcohol*

* Common rubbing alcohol is 70% solution, add appropriate water, about 2 spoons per 1 spoon should do