[watch one's dust] or [watch one's smoke] {v. phr.}, {slang} To notice your quick action; watch you do something quickly.
* /Offer Bill a dollar to shovel your sidewalk, and watch his smoke!/* /"We'll have your yard cleaned in a jiffy," the Boy Scouts told Mr. Truitt. "Watch our smoke!"/* /"I can go to the store and be back in five minutes," bragged Tom. "Just watch my dust."/