"shining their shit"

Shit - human excrement is a waste product, made of, well composed of whatever an individual last ate - in a period of time that it takes a human body to fully process food

Waste - something that is no good anymore and should be thrown away, disposed of... *

Just "shining their shit" is an exercise in futility or pointlessness, usually unknowingly so. People who are trying to improve something that is beyond saving.

* my metaphor isn't considering green ecology or saving the planet by recycling. Which, of course, is a good thing, as any fuel know! **

** ...as any fool know(s) or should know.