I support the rotor between two 2x4s and hit the studs with a 12 lb sledge with an aluminum plate in-between to protect the threads, one whack on each stud is all it takes.
When reseating the studs in your new rotor don't do it with the wheel installed, you can damage it. Best to use a bunch of washers and a lug nut turned upside down to suck 'em in. This is where an impact wrench pays for itself rapidly.