superman shaves with heat vision but as for cutting his hair, there are a few possible explanations. 1.)since he's superman after all, he probably is strong enuff to cut his own hair 2.) (which i believe might be closer to the truth) he has some sort of psionic control over his body's molecules, as a result he has "selective permeabilty"(anat. and phys. 101 for that ass) meaning that he can let whatever he wants pass thru his bio shield at his whim, for he has been shown to recieve injections in at least one elseworld title that i know of.