I have had success removing altenator pulleys with a good air impact wrench,and nothing else-I just wrap a rag around the fan and hold it by hand,or use heavy gloves,-I've wrecked a few trying to use an allen wrench in the shaft,and holding it in a vise and using a box wrench--but the impact usually zips it right off with no sweat--
I had to change a good many pulleys at the parts store on a saturday afternoon--many stores would not sell someone an altenator just because the pulley was the wrong one for the application,I would just zip the customers old pulley off,and install it on the new altenator--my boss freaked when I took one altenator apart and "clocked" it,so the plug would be in the right spot!--guess he had no faith in my mechanical abilities!--but he liked the 150 bucks I put in the register by "saving" the sale--..