Didn't you know? Some people push up glasses with their middle fingers and two fingers tucked in. [he demonstrates] And some push with both their middle and forth fingers. [another demonstration]

Yet others push by cradling the lense between their thumb and index fingers. [demonstration!] And some others push by pinching the frame. [push push push Grinnnn.] Highly subjective. It's just a matter of finding which style of push suits your personality.