--> most of the standard cells are "already" designed in one technology...using that the new ones are done in any technology. there are programs to do that. a small number of cells are optimized using hand. the DRC clean up is done manually not the actually layout.
--> Power bus width depends on intended application(speed wise)....9Track, 12Track are used. Power bus depends on the voltage of the final design and speed.
--> skill is used for simple scripts for manipulating layouts but overall layout is not done using skill