Once a coin has as much circulation damage as the subject coin has, you pretty much can't hurt it.
It's worth 5c. If you lightly scrubbed it with steel wool, it would still be worth - wait for it - 5c. So a toothbrush won't hurt it.
Now if it had numismatic value, then the toothbrush is a really bad idea.
45 year / Life ANA
member (joined 12/1/1973)
Life member: Numismatics International, CONECA
Member: TNA, FtWCC, NETCC
Owned by four cats and a wife of 35 years (joined 1983)