No ginding. He vaporizes his whiskers by focusing his heat vision in a concave mirror held in his right hand that concentrates intense heat on each individual hair. In order to avoid a streaky sunburn pattern he moves the mirror at superspeed providing enough heat to singe each hair but moving on before his skin is affected. Or maybe not. He could use his superstrength to simply push the stubble back below his skin's surface. No, wait, that would give him an unbearable number of ingrowns. I know. He exits the earth's atmosphere and then singes the whiskers off on re-entry. No, that would make him bald too. I'm sticking with heat vision focused on the stubble. If not, he goes to the Fortress of Solitude, spashes water on his whiskers, steps out into the sub-zero temperatures of the Artic, allows the whiskers to freeze and breaks them off-the ultimate cold water shave. The real question is where he finds all those phone booths to change in these days. I haven't seen a real phone booth in years. They're scarcer than a barber with a straight razor in his hand and a customer in the chair.