Green’s Dictionary of Slang

1. (also dust down, dust someone’s lamps) to deceive, to mislead.

1902		J.H.M. Abbott Tommy Cornstalk 72: I carn’t make out w’y the English Government gives these drivers on our transport four-ten a month w’en they could get ’em for a quid, an’ dust ’em down over that too. ’Y mus’ keep niggers down.
1950		P. Hoskins No Hiding Place! 190/1: Dusting his lamps. Supplying a false lead.

2. (US) to tease, to hoax.

1956

E. Hunter Second Ending 267: ‘Oh, come on, man, you’re dusting me.’ ‘I kid you not.’.