Definition
To do something extremely quickly and perfunctorily.
How People Actually Use It
"Whipping through the glass" means that he's mixing cocaine to make crack in a glass pan. "whipping" means to stir a mixture. And "through the glass" refers to the glass pans usually used in the process of making crack cocaine.
"Person 1: "damn nigga it stanks in here! Person 2: "I makin crack nigga" Person 1: naw nigga you doin it all wrong, you gotta whip it through the glass nigga!" Person 2: "I know nigga! actin like I don't know how to make this shit?!" Person 1: "I whip you through that glass if you don't stop talkin like that!" Person 2: "righhht""
Source: Urban Dictionary