schloss, "...of the first water" probably is a common expression. (I don't remember ever hearing it before, BWTFDIK?)
I was trying, (obviously unsuccessfully), to make a joke involving your reference to "picking nits" -- which expression, taken literally, (I think), refers to the manual method of "delousing," i.e., picking individual louse eggs ("nits") from one's hair, one at a time.
It coulda been funny. It just wasn't.
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