Where have you heard or read 'blunder buster'?
It's new to me.
Rover
There was an article in "COSMOPOLITAN" called "The biggest communication mistakes women make". "Blunder buster" refers to not making them.
It is a play on words, referring to the old gun, the blunderbuss.
As you said, the article is offering advice about how to "bust" your "blunders".
You possibly could say "to bust a blunder" but it is not an idiom and you lose the play on "blunderbuss". It would probably just sound strange.
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