Use 4 fingers, two on each hand.
Install disc and pressure plate, LIGHTLY install pressure plate bolts JUST tight enough to allow you to slide the disc around and yet not allow it to fall. Center the disc to the pressure plate using your fingers, then finish tightening the bolts. It works, and it's fast!
Optional tool: 6 or 8 fingers, or 3 or 4 on each hand.