I suggest you don't use a shifter, or even a fixed open-end spanner, on a rare nut which may be very tight. At best you'll make the nut look old and beaten up: the jaws on those types of spanner deflect considerably under load. Use a deep 6-point socket, or a good-quality ring spanner, if you want to keep it looking nice.
A rattle gun does the best, quickest job with the least damage. A breaker bar is an acceptable substitute if you have a good enough way to hold the base of the machine stationary. Because a deep 6 point 1.25" socket will be expensive, I'd seriously consider a ring spanner, but it would have to be a high quality one that fits really well on the hexagon. Do not use a mallet on the other end of the ring spanner: 12 point spanners are just not stiff enough to stand that without springing out of shape and damaging the hexagon.
